holyshit! i got it
I took a hint from blind123's instructions. Since I'm using xp, I ignored all that stuff about taking ownership. Here's what I made sure to do differently this time:
1 - plug the phone into the PC and turn it on normally.
2 - dial the ##DATA#, click the first item in the list and select "edit". When it asks for the code, I gave it 000000 twice and it said it was going to reboot. I immediately pressed and held both volume buttons and waited for the phone to enter download mode
3 - I started up the memory dump program just as I had done 100 times already and made a dump and it actually worked this time.