Just got word from Martin about a aew MSI KT3 Ultra BIOS that fixes a LOT of problems! Here's what he's saying:

The date on it says 3/20 but it was just posted by MSI after passing through extensive testing.

MSI just posted the 5.21 BIOS which fixes a LOT of overclocking related problems. Before flashing to this BIOS I was not able to go above ~160 FSB and after it I maxed at 187. Also with the shipping BIOS I wasn't able to get the +33 function to work at ALL! Download MSI KT3 Ultra BIOS v5.21 and see what the users say about this BIOS in the Mods4me forums