Ok,
I'm running under Vista too, and I believe your problem is most likely a permissions problem. Try giving your limited user read/write permissions to the BeerSmith directory, its subdirectories and the files underneath.
On my Vista machine, this was not a problem if I installed BeerSmith as a limited user and ran it, but if you upgraded to Vista in place or installed as an administrative user first I could see a permissions problem as a possibility.
On the next version, I am planning to separate the data directory from the program directory to avoid this problem.
Cheers!
Brad