Hi Steph,
Can't answer your question directly, but I've seen that kind of message too... I saw it when I was trying to uninstal a copy of Labview, and I kind of recall that the problem had something to do with the length of paths keys in the registry had... The fix was a little exe from NI that went through and deleted specific registry keys separately to the main uninstaller...
Maybe not too much help to your problem, but maybe suggests a registry type error?
hope this helps... a bit
Regards
JB