Fish,
I honestly have not seen this type of problem before, but my quick suggestion would be to save your data off (use the Export command to export your recipes to a BSM file) -- then reinstall the program but this time install it to a directory under your main user's "Documents" directory - for example "C:\Users\USER_NAME\My Documents\BeerSmith" where USER_NAME is the one you regularly log in to.
Then run the program as usual and import your recipes back in.
I'm running Win 7 64 bit here on several machines with no problems.
Thanks,
Brad