empty files (zero bytes)

[Saddy]

After a year of usage or so many files on my encrypted hdd are now empty (zero bytes). Since there are many of them in different (random) folders I'm pretty sure I did not empty them myself accidently. SMART values of the drive seem o.k. (5 months usage). I notived that when there are empty files, then the whole directory is affected, so all files in this dir are empty. If you need further details please let me know.

=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate 0x000f 113 099 006 Pre-fail Always - 56966640
  3 Spin_Up_Time 0x0003 094 094 000 Pre-fail Always - 0
  4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 672
  5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail Always - 0
  7 Seek_Error_Rate 0x000f 067 060 030 Pre-fail Always - 6142791
  9 Power_On_Hours 0x0032 097 097 000 Old_age Always - 3451
 10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0
 12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 671
183 Runtime_Bad_Block 0x0032 100 100 000 Old_age Always - 0
184 End-to-End_Error 0x0032 100 100 099 Old_age Always - 0
187 Reported_Uncorrect 0x0032 007 007 000 Old_age Always - 93
188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0 0 0
189 High_Fly_Writes 0x003a 100 100 000 Old_age Always - 0
190 Airflow_Temperature_Cel 0x0022 070 060 045 Old_age Always - 30 (Min/Max 21/30)
191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always - 0
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 10
193 Load_Cycle_Count 0x0032 100 100 000 Old_age Always - 867
194 Temperature_Celsius 0x0022 030 040 000 Old_age Always - 30 (0 16 0 0 0)
197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0010 100 100 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always - 0
240 Head_Flying_Hours 0x0000 100 253 000 Old_age Offline - 3494h+16m+40.778s
241 Total_LBAs_Written 0x0000 100 253 000 Old_age Offline - 37713646382758
242 Total_LBAs_Read 0x0000 100 253 000 Old_age Offline - 81502538966889

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: cryptsetup 2:1.6.1-1ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-39.66-generic 3.13.11.8
Uname: Linux 3.13.0-39-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.5
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Nov 20 19:34:21 2014
InstallationDate: Installed on 2014-05-19 (184 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
SourcePackage: cryptsetup
UpgradeStatus: No upgrade log present (probably fresh install)
crypttab: # <target name> <source device> <key file> <options>