Hmm ... This is a general Windows message beyond the scope of the program (hence me).
If you look at the third line (the "(C:\Users ...)") you could :
1. Save that user.config file which is in there (it might be of use if 2-7 don't help);
2. Delete that folder entry as shown;
3. Restart 0.9u-15.
4. If this doesn't help re-do 2 but note the name of the folder might be different now;
5. Find a similar entry for 0.9u-14a and delete that one;
6. Restart 0.9u-14a and don't change any settings;
7. Restart 0.9u-15.
Please note that "re-install" XX as such does nothing at all, so don't waste you time on that !
If all doesn't help, send me the user.config you saved at step 1.
Peter