In all likelihood, this is a Qt issue, so try with the new version here:
http://users.ugent.be/~pbienst/pub/mnemosyne-20120709-setup.exe
> 2) For me Menmosyne 2.0 is now very stable, I go through approx 200 cards a
> day, often adding new cards. Total ~ 10.000 cards. Sometimes (once a week?
> max), out of the blue comes an error message (I have enclosed two examples,
> one came after about 40 cards, the other after about 200).
This new version might also help with the I/O error.
As for the latex error, is it reproducible, i.e. does it always happen on the
same card? Does the card contain latex?
Peter