Migration assistant problems - 10.4.11 to 10.6.4

We just purchased a new Mac Mini (10.6.4) to replace the old Mini (10.4.11). I've tried to do the Migration Assistant multiple times this week. I can get as far as the "transferring data" message with a progress bar and a time estimate. The problem: After 5-12 hours, the time never changes! Today I even tried transferring just a few files - 1.6GB - just to see if it would work better with fewer files. The time estimate told me it would take 13 min. After 5 hours (we left the house), the time estimate had changed...to 26 minutes! What am I doing wrong?

Here's what I've done so far:

- Updated OS software on source computer.

- Installed 2008 Migration DVD CD share software update (running 1.0.6 on the source computer)

- Both computers are set to never sleep or go into energy saver mode. Even turned off screen savers.

- Connected computers via Firewire 400/800 cable - 5 or 6 attempts with no progress

- Also tried wireless connection - 2 attempts, both time network connection failed.

- Tried the "Internet Sharing" instructions on the Apple Support site. Didn't work either.

- Source harddrive mounts on new computer's desktop. When I double click on it to try manually transferring....new computer freezes up and I get the never-ending spinning circle.

I'm only trying to transfer about 50GB. Judging from others' posts, that should take me 2-3 hours. Right? I've run migration assistant on other computers before and never had any trouble. Is there some update I'm missing? What am I doing wrong?

Thanks for your help!