So after returning from holiday I thought I'd get the "proper" 8-pin connector hooked up as I'd been using a 6-pin to 8-pin adapter whilst on holiday. So about an hour ago I switched to one of the 8-pin to 8-pin modular cables that shipped with my TT PSU. 1st attempt, power up fine, all PSU LEDs green, but black screen, no POST (?) 2nd attempt, same again, and I notice that GPU fans are spinning up, dying down etc. 3rd attempt, try other 8-pin cable, exactly same again 4th attempt, try another 8-pin output from PSU, same again So I went back to the 6-pin cable/adapter I'd been using and PC booted up fine first time. So there must be something wrong with the 8-pin cables, right? So I tried one of the 8-pin cables with the adapter, and same again - no POST, black screen Went back to the working combo, and *gasp* no POST, black screen WTF?! Reset CMOS, and now I have a 6-pin and 8-pin cable (both TT modular) working fine - y'know, the combo that refused to work the last 6 or 7 times I tried it, lol. So what do you guys think... possible GPU problem, PSU problem, or just one of these annoying quirks that can never be explained? I've run umpteen stress tests, both GPU and CPU, and have a hexcore CPU running at 4.3GHz currently, and there are no problems with my system, so I'd say it's very unlikely to be the PSU. PSU is almost 4 years old but iirc it has a 7 year warranty (which I probably voided by replacing the PSU fan, lol!).