Hi everyone. I am new here =)

I have a question, i hope someone knows what the problem might be.

When I HTT overclock my little Sempron 140 @ Athlon X2 4400 to 240x13.5. I noticed something weird in bios and CPU-Z. Memories change from Dual channel to Single Channel. Does anyone have any idea why it is so?
Could it be that it is just a buggy bios version? Run with the latest bios version 1.50

My motherboard is ASRock > Products > 890GM Pro3 R2.0
And i have Corsair XMS3 4GB DDR3 PC3-12800 1600MHz (2X2GB) (CL9) (CMX4GX3M2A1600C9) memorys

Sorry for my bad English. But I hope you understand what i mean