Hi,
first make sure that you have installed the latest erratas, especially Univention Corporate Server 4.1 erratum 211. If this doesnt solve the problem check How to deal with s4-connector rejects.
Please post meaningful error messages and log extracts in case you need more help.
To answer your question regarding the rollback to a previous point release: This would require to roll back all involved packages. I dont know if there is an easier way.
Best Regards,
Dirk Ahrnke