At least for me, the problem still persists on Lubuntu 12.04, Kernel "3.2.0-30-generic #48-Ubuntu SMP Fri Aug 24 16:54:40 UTC 2012 i686 athlon i386 GNU/Linux", all updates installed up to now. In the "dmesg" log, i got the error messages below. However, my disk is certainly not full (> 100 GB left on "/", no other partitions mounted except for swap). No other error except for an ACPI error can be found in the log.

Relevant Dmesg log part:
---------------
[ 3571.816762] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.816781] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000000])
[ 3571.817002] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.817011] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000000])
[ 3571.817232] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.817240] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000000])
[ 3571.817463] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.817471] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000000])
[ 3571.817751] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.817761] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000001])
[ 3571.817978] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.817987] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000001])
[ 3571.818205] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3571.818214] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000001])
[ 3576.816516] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.816535] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000002])
[ 3576.816761] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.816770] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000002])
[ 3576.816990] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.816999] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000d])
[ 3576.817284] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.817293] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000003])
[ 3576.817512] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.817520] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000003])
[ 3576.817739] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3576.817748] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000011])
[ 3581.816755] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3581.816775] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000004])
[ 3581.816998] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3581.817007] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000013])
[ 3581.817308] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3581.817317] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000005])
[ 3581.817536] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3581.817544] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000017])
[ 3586.816475] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3586.816495] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000006])
[ 3586.816729] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3586.816739] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000020])
[ 3586.817088] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3586.817098] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000007])
[ 3586.817326] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3586.817335] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000021])
[ 3591.816661] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3591.816680] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000008])
[ 3591.816901] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3591.816911] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000023])
[ 3591.817224] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3591.817233] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000009])
[ 3591.817451] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3591.817459] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000024])
[ 3596.816663] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3596.816682] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000a])
[ 3596.816902] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3596.816912] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000002c])
[ 3601.816652] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3601.816671] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000b])
[ 3601.816890] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3601.816899] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000002d])
[ 3601.817214] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3601.817223] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000c])
[ 3601.817440] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3601.817449] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000050])
[ 3601.817732] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3601.817741] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000d])
[ 3606.816622] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3606.816641] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000e])
[ 3606.816945] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3606.816954] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000000f])
[ 3611.816567] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3611.816585] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000010])
[ 3616.816664] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3616.816683] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000011])
[ 3621.816598] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3621.816617] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000012])
[ 3626.816473] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3626.816492] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000013])
[ 3631.816356] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3631.816375] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000014])
[ 3631.816706] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3631.816716] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000015])
[ 3636.816262] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3636.816276] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000016])
[ 3636.816439] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3636.816444] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000017])
[ 3641.816740] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3641.816759] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000018])
[ 3641.817069] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3641.817079] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000019])
[ 3646.816480] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3646.816498] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001a])
[ 3646.816823] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3646.816833] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001b])
[ 3651.816487] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3651.816505] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001c])
[ 3651.816840] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3651.816850] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001d])
[ 3656.816553] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3656.816583] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001e])
[ 3661.816201] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3661.816213] ecryptfs_writepage: Error encrypting page (upper index [0x000000000000001f])
[ 3661.816392] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3661.816397] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000020])
[ 3661.816545] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3661.816550] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000021])
[ 3666.816262] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3666.816274] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000022])
[ 3671.816279] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3671.816289] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000023])
[ 3671.816448] ecryptfs_encrypt_page: Error attempting to write lower page; rc = [-5]
[ 3671.816453] ecryptfs_writepage: Error encrypting page (upper index [0x0000000000000024])