TSM 6.1 was pretty much a complete rewrite of TSM. It’s been out for a year, and there are still OS kernel panics, TSM Server crashes, data loss, and general reliability issues. 6.1.3.0 was retracted because it introduced badness, and was replaced with 6.1.3.1.

Honestly, I would recommend people stay at 5.5 until things with 6.x prove to be more reliable.

Some good references for fix history:

http://www-01.ibm.com/support/docview.wss?uid=swg21177831

Developer Works: TSM 6.1 APARs