I had the fans connected to the mobo. And the leds to the PSU via molecs[strike][strike][strike][strike][/strike][/strike][/strike][/strike]
are case fans connected to motherboard or molex 4 pin from PSU or otherwise?
most likely you accidently disconnected cable from power switch to motherboard
or possibly the ATX/EPS 4/8 pin 12V cable to motherboard (near CPU socket)
if that fails read Toms FAQ for diagnosing non starting PC's
http://www.tomshardware.co.uk/forum/261145-31-perform-steps-posting-post-boot-video-problems
regards
Mike Barnes