Installed new video card and all hell breaks loose...

The past:
Used Empire EFI to install myHack onto Intel DG31PR, Q6600, with NVidia 8600GT
No problems. Worked since SL came out...

The present:
So I decide to upgrade the graphics card. Minecraft and Civ V could run a little faster. I decide on a GT240 DDR5. Come home, slap it in. Sometimes it boots OK, sometimes I get a kernel panic, and sometimes it just hangs. Civ V never works, so I decide its going back.

I put the ol' trusty 8600GT back in, and now it won't boot SL. I'm getting the blue screen that flashes sometimes. I try booting with EFI Empire, and I get this error - ACPI Table not found: DSDT.aml

From what I've read theres a problem with the video card kext, or boot string. But like I said, it worked fine for years. Would putting a new card in remove the old driver? And I thought that these cards just worked with myHack, and nothing special was needed to be done.

I've booted with myHack and -x -v and I don't see any obvious errors.

At this point, I'm not sure what the next step is. I can't boot into it, my secondary mac partition (running Leopard) won't boot either. Windows boots, but I can't write to that volume. I can extract the drive and hook it to a real mac to edit files if I need to.

Is a reinstall in my future?

Thanks for your help!