When I exit out of XBMC, the TTS will work and then VC crashes.
This statement by itself makes no sense to me based on what you have shared with us previously, which was that VC would crash immediately when you used a command that had TTS actions in it.
When you are quoting something from another page please use the
quote tag
or put "quotes" around it, which will make it easier for others to understand your post.
As for the possibility of there being a confilct with XBMC I suggest to do some tests on your own since you are the only person who has access to your computer and therefor you are the only person who can determine if adjusting these settings will make a difference.
It doesn't make too much sense to me though that this would be an XBMC issue since you only have problems with one of your TTS voices and not with the Microsoft voice, but then again, computers often don't make much sense, and also I don't really know if your tests were performed the same way with both voices.