After a lot of digging I found a few things…
1. there was a problem in the database in the wp_user2role2object_rs table. A couple of groups had entries with 0 for users I removed the group's section roles and then put them back, which seems to have taken care of one problem. Posts are no longer being assigned to the default author.
2. I already had the RS cacheing turned off so I don't see that this was the issue.
3. I changed the default category and tested again. The posts went to the new default category so it's definately related to that setting somehow.
4. I did disable the plugin and I was able to save a post as a contributor to the category I selected.
5. Once I gave contributors access to the default category I was able to save a post, reselect categories, then resave with the correct category selections. It seems to be related to the initial save process.
My temporary work around is to give editors and contributors to the default category but this has implications for the editors who rely on recieving an email notification when a post is submitted for review in the category they manage. It's not realistic to expect the contributors, who are not terribly savvy, to save, select categories, and save again.
I have disabled the WP autosave function because it was causing problems when posting in IE.
If you have any ideas or would like to look at my install(it's a complex one) let me know.
Daisy