Comment 2 for bug 773495

From both your description your stack trace, considered together, I can see that this bug is actually a duplicate of bug 529714. (That bug's title is misleading--it's actually not specific to RhythmBox at all, and there are several bugs marked duplicates of that bug in which the crash occurred in Banshee on launch--in fact, in Ubuntu 11.04, it appears to primary occur in Banshee.)

You'll notice that in bug 529714 there is a workaround recommended. I recommend you try this. I'll post more about this in your question (https://answers.launchpad.net/ubuntu/+source/banshee/+question/154805).