I'm having some issues since I switched my psu recently. When I first plug it in, and hit the power button, I get a quick fan spin, then nothing. The power light and ram light (on the mobo) stay on, but nothing else. I let it sit a few hours, and it will power up.

My 12v line is reading between 12.9x and 13v! It is a 400watt PSU with a 18A rating on the 12v line.

Here is my system:
P4 2.8 ghz hyperthreading
4x 512 sticks of Corsair XMS Pro dual channel DDR memory
Intel P875 motherboard
ATI AIW 9800 Pro
ATI TV Wonder Pro
SB Audigy 2
2x Western Digital Raptors
Toshiba DVD
Plextor DVD+-RW
Floppy
3 case fans plugged into the mobo
CPU fan plugged into the mobo

My last two PSU's with this setup were a Enermax 651 and a PC Power and Cooling Deluxe. No problems with thouse (other then noise).

Any ideas? Too weak of a PSU?

What PSU? You never mention the make & model.

ATI TV Wonder Pro is a PCI card?

It's a SilenX iXtrema Pro 400. I believe it's Fortran based.

Yeah, the TV Wonder Pro is a PCI card.

The 12V line might be pushed to its limits. If you think the high load may be the issue, try a systematic troubleshooting approach:

1) unplug your PSU from the AC
2) remove all peripherals except what you absolutely need -- like just 1 stick of RAM, 1 VGA, min # of HDDs.
3) boot the system
4) If it boots with this min load, then turn off, plug PSU again, and add a component.
5) Reboot. If successful, repeat, adding one item at a time.

Chances are a couple fewer devices will ensure consistent start every time. My guess is you are borderline on the current surge at startup. You might have to move to a PSU with higher 12V current capacity.

PS -- high 12V readings often happen when the 3.3V + 5V lines are drawing very little current. You probably should check this voltage at a 4-pin molex output with a multimeter.