Am 17.06.2012 19:14, schrieb VanguardLH:

http://www.intel.com/content/dam/www...ion-update.pdf
Errata (sheet 3 of 4), page 11
Number 54

This points to a processor erratum fixable by a BIOS workaround.
I have looked at Gigabyte, and, although not clearly visible, they do
have a fresher BIOS.
I was running f10c since about February, now they call it (just) f10.

This indeed fixed the problem!

Thanks for your help.