i replaced pcu fan now monitor wont work.. help!

hey guys,

Ok so here's the deal... I've got a reasonably new (1yo) computer i built... it's asus a8nsli with athlon 64 4200+ chip, 2gigs memory etc, evga 512 mb vid card...
anyways i was having issues with the pcu fan, it wasn't operating fast enough for my computer to be happy and i kept getting warnings when i'd boot up...
so after 2 days of being annoyed i went and got a new heat sink/fan

i installed the heat sink and fan ... and now my computer will turn on but my monitor won't read anything from the video card. like when i turn my monitor on... it turns itself off after the power light blinking for a couple of seconds i disconnected/reconnected everything i could think of ... and the pcu fan, vid card fan, and all my case fans are powered... and the green light on my motherboard is lit up...
also one thing i noticed, was the red led was lit on the front of my case which I've never seen before...

anyway help is GREATLy appreciated

thanks a lot guys
Brandon