I recently installed Kubuntu Jaunty on a new drive, using Ext4 for all my data.
The first time i had this problem was a few days ago when after a power loss ktimetracker's config file was replaced by a 0 byte version . No idea if anything else was affected.. I just noticed ktimetracker right away.
Today, I was experimenting with some BIOS settings that made the system crash right after loading the desktop. After a clean reboot pretty much any file written to by any application was 0 bytes.
For example Plasma and some of the KDE core config files were reset. Also some of my MySQL databases were killed...
My EXT4 partitions all use the default settings with no performance tweaks. Barriers on, extents on, ordered data mode..
I used Ext3 for 2 years and I never had any problems after power losses or system crashes.
Did anyone else have a similar experience?
Update: Anyone experiencing this issue please comment on Bug #317781
Also note that some recent Seagate drives have some firmware issues that are not related to ext4 in any way. Look here and here for more info.