Since installing NITDroid 0.0.8 the Audible Beta player seems to be working.

I doesn't appear in the Marketplace, but you can get it from http://groups.google.com/group/audib...oid-beta?pli=1

There have been some problems downloading Audible books to Froyo handsets. The best solution seems to be to set the quality to enhance (aax) before starting.