Comment 3 for bug 1255531

I have done a memory test as suggested in https://help.ubuntu.com/community/DebuggingSystemCrash - sorry for not reading it earlier.

Errors were found at four addresses in the memory area of the second 4 GB module. After removing it and running with only the first 4 GB, no more errors were found.

I will test for a week without the second module and report back if the freeze is solved with that.

For anyone with a similar problem:
It seems really worth running the memory test! With 8 GB it took just about 50 min for one complete pass.
Just press (right) shift on startup to get the GRUB boot menu, and start the memory test from there.

Cheers,
Torsten