Can't Overclock after flashing BIOS

I am using a Gigabyte P35-DS3R mobo for my Q6600. Funny thing is that after using Gigabyte's own updating BIOS tool, I tried to overclock my rig to 3.0 ghz. What happened? The BIOS does not recognise the overclock settings even though I have save it and was running it! Isn't it strange?

At the moment, I am running on a beta bios of F13a. Question is whether there are any problems with the BIOS at all. Oh well, I figure it out that after flashing the BIOS to the F13a firmware, I cannot right click on the programme menu to reorganise it. Strange, isn't it? I wonder whether anyone else encountered this problem.

Update 23/10/2008:

After changing the graphics card and memory, it appears that I can overclock my pc again! Yahoo!!!