Thanks for the help , the fstab is still ok

I figured out what was wrong. Apparantly the filesystem was corrupted.

I ran:
fsck /dev/mmcblk0p2

Which stated a lot of errors and fixed things up using the journal of the ext3 filesystem ...

After that I rebooted and now everything is ok again.

I think I had a sw_rst reboot while another process was maybe writing to the partition. In each case the reboot caused the partition to be in a corrupted state. fsck fixed it all.