The problem seems related to the way ubuntu hibernation work.
The problem disappeared after installing "tux on ice" version of kernel suspend to disk implementation (using version at ppa:tuxonice/ppa):
$> uname -r -v
2.6.32-22-generic-tuxonice #36~ppa2-Ubuntu SMP Sat Jun 5 02:21:24 UTC 2010
The problem seems related to the way ubuntu hibernation work.
The problem disappeared after installing "tux on ice" version of kernel suspend to disk implementation (using version at ppa:tuxonice/ppa):
$> uname -r -v 22-generic- tuxonice #36~ppa2-Ubuntu SMP Sat Jun 5 02:21:24 UTC 2010
2.6.32-