I have a 4000T that is doing something similar. Some of the cards disappear from my early boot menu and no longer function after booted. It only happens after my 4000T is warm though. I have thought about getting some of that electronics freeze spray and spray a components and reset, repeat until working. I wonder if Radio Shack has some. I just bought a new 400W AT power supply hoping it might fix the problem but it didn't make any difference. My 4000T is an (early) Rev 2 with 40.70 ROMs and my main accelerator is the CSMK3 which is very similar to yours. Hmmm.