Hi Nukevil,
Had a very similar problem the other day, it might not be related to yours but a few days ago i opened one of little dell desktop(hate working on cases with no space).
Done the little upgrade myself and when i put everything back same problem no power at all.
Tried all, then checked where the power button is inside the case the little wire which was connected with power button with motherboard was out.Imust knock it out while working.Hope its simple as that.
Good luck (sorry forgot to tell the light came out and fan was on for a few sec too)