Dead logic board?

I have a 15 inch macbook pro that's about three years old (just out of warranty) and I'm experiencing some weird issues.

1. When I can boot into the hard drive it works for about ten minutes and then I get a frozen (spinning) beachball cursor and can't do anything but move the cursor.
-If I run disk utility the hard drive completely disappears off the list after about 10 minutes. It's a brand new, correctly formatted HD so I know that's not the issue.

2. When I go to startup I get the blinking question mark folder. If I shut it off and leave it alone for a little while I can try again and it will usually find the HD and then I have the previously mentioned problem.

3. Sometimes (it's inconsistent) when I go to boot from a cd the cd will simply be ejected and I'm left with problems 1 or 2. The track pad is not pushed in.

I have reset the PRAMs more times than I care to count, have uninstalled and reinstalled (albeit from a time machine backup) and have attempted to try a ubuntu live CD I made, but the CD is constantly ejected back at me. (It's quite aggravating).

I think it's a bad logic board, but I'm praying I'm wrong. Any ideas?

I would be more apt to believe you have a bad HDD and an intermittently flaky Superdrive.

The hard drive should be easy (and cheap) enough to swap out. I would start there.

Agreed. The blinking question mark and Disk Utility results strongly suggest a failing hard disk or bad/loose HD cable.

That's what I thought, so I literally replaced the HD yesterday with a brand new WD 500gb SATA drive. Still having the same problems.