Hi nummymuffin,
I asked around, and there aren't any known issues with running our diagnostics on SLI enabled systems. However, I will ask again about Quad-SLI configurations (or SLI with Dual-GPU graphics cards) like what you appear to have.
If you have had recent BSOD's (Blue Screen of Death), I would take a look in the Performance tile for your version of PC-Doctor Toolbox. It should provide some explanation for what caused the Blue Screen, and offer some suggestions for a possible resolution. If you would be willing to share, I would be interested to know what our software says about them.
I will get back to you as soon as I have found any information, but I am beginning to think that this is a false positive that we will need to investigate further.
Thanks for your help,
Kris