One other thing you might try is to delete the directories
c:/Users/win_user_name/AppData/Fritzting and
c:/Users/win_user_name/My Documents/Fritzing
(note AppData is a hidden directory so you need to enable show hidden directories in explorer in order to access it) Fritzing uses these 2 directories for tmp and your parts files but does not delete or over write them when you do the unzip, so if something has gotten corrupted in them that may be your problem. If the directories aren't present Fritzing will recreate them. Otherwise the software works for lots of other people so there has to be something going on with your system as this isn't one of the common problems (such as missing C runtime DLLs) that have occurred before. Good luck!