It does sometimes keep a screw up forever once screwed up. What I do (and when it hangs because of bad new parts) is clear the two Fritzing user directories (note that this will destroy all your sketches and parts so you may just want to move the directories aside rather than delete them!). They are
(which is a hidden directory so you need to have show hidden directories set in explorer) and
(where username is your windows account name). Deleting and reinstalling Fritzing doesn't touch these directories (to preserve user data during upgrades) but if you delete or move them aside Fritzing will recreate them and hopefully work better. If it doesn't I'd suggest uninstalling the Fritzing and reinstalling in case you have a bad install but I'm thinking something is probably corrupted in the user directories.