This is a year old... but I have had the same issue, after performing the BIOS mod. The fix for me was to reload the default BIOS settings within the modded BIOS, not reverting to stock. This means that there is some setting within the modded BIOS that is causing the issue. My guess is that it is electrical interference from somewheres, probably the CPU. I hadn't overclocked, but I did set the CPU to Turbo Mode. I am going to try to set everything back the way it was, besides turbo mode, and see if that fixes the issue. If so, I'll post such here.
At the same time, if anyone knows more about the modded BIOS' settings and would like to chime in... please feel free. There are a lot of variables to consider.