Matt, I have never personally had that problem, but I did a bunch of e-research and your situation doesn't look all that good.

Hopefully it's something easy like the oil filter...or maybe you didn't prime the oil right before restarting it.

Good luck.

V6Z24.com :: View topic - No oil Pressure 2.4l

This one is from a BMW site but I'm sure the troubleshooting would be the same considering they are hydraulic lifters:

Engine Knock & Oil Pressure - BMW Auto Repair Advice

The main things I would look at are the oil filter...then drop the oil pan and check the pick-up tube and screen for blockage.

Good luck man, low or no oil pressure seems like a pretty serious condition.