CONFIRMED that there were changes to the the framework.jar between 3.29 and 3.31. You should NOT use the 3.29 Market hack on 3.31 - I'm working on a new hack zip.
I opened up the framework.jar file between the two and did a diff - several smali's were changed.
DAP: Cowon D3, Sansa Clip 2GB Rockboxed
Cans: Sennheiser HD 600, Yuin PK1, Sony MDR-V6
PC: Ubuntu Jaunty x64 w/Creative Audigy2 ZS