Post Code F2

I have an old PC that was working and I moved it to a mini case to make it a server.

Now after I moved the components I am getting post code F2, stuck for a few seconds and reboot.

Motherboard: Gigabyte ga-880gm-usb3 CPU: AMD Athlon II x4 965 BE GPU: AMD 7770

The BIOS as far as I remember is Award bios, and I don't find code F2 documented.

Any idea what does it mean?