Really does sound like a compatibility issue, mobo bios is not identifying the processor properly, spec should read 9x1333Mhz, not 6x333Mhz.
There are two versions of the E8400 cpu (Sspec SLAPL/C0 stepping and Sspec SLB9J/E0 stepping), according to MSI website you need bios 7380v20 for the C0...