there was a known error with the RealSpeak TTS engine a while back that if you logged into the desktop and while logged in a call came in that used TTS resoruces, if you logged out it would kill the TTS engine which, in turn, pulled Unity down with it. An updated TTS engine from the RealSpeak folks fixed this issue.
Which build of Unity 2.x are you on? Are you using RealSpeak? If so, you can download the new RealSpeak TTS engine that fixes this off CCO at:
http://www.cisco.com/kobayashi/sw-center/sw-voice.shtml
follow the link for "Other components"
Jeff Lindborg
Unity Product Architect/Answer Monkey
Cisco Systems
lindborg@cisco.com
http://www.AnswerMonkey.net (new page for Unity support tools and scripts)
