For the last few month's, I've been experiencing a strange problem with my
'mail server' running Debian unstable on a 2.6.7 kernel.
Once in a while, random files get corrupted. I sometimes get crc errors
opening a (tar.gzipped) man page, or when doing apt-get updates. Also
occasional application crashes that can mostly be resolved by reinstalling
the package (apt-get install --reinstall).
I can verify the file has been altered (it happens sometimes a textfile is
affected, and with vi I can correct the mistake, for exmaple 'if' magically
becoming 'of'). The timestamps of the files are not changed.
Strangly enough I never get read or write errors in dmesg, and disk scans
using 'e2fsck -fccv' (non-destructive surface scan) never turn up bad
I ran an overnight memtest (memtest86) too, to no avail.
The disk is not new, but also not battered. The PC is an old HP Kayak
Pentium II 300Mhz with 320Mb ram.
All partitions are ext2.

Any idea's what might be the problem, or what other diagnostics I can do to
come closer to the source?