I'm having the same problem, but I can't get the Save folder to change. Everyone I select gives the same message. I'm running Windows Vista with multi-user accounts. Any other ideas?

Delete FW's preferences folder when FW is properly closed... more info here: FrostWire - Permissions Error?

And for extra info about how to find the prefs folder, check out this thread: LimeWire Pref Folder in Vista
The info there refers to LimeWire (LW) but info's the same for FW

Deleting the prefs folder will revert all settings within tools > options to default, so you'll need to go back through tools > options afterwards & reset things If you're not sure of your settings, go through & make a note of them before deleting the folder.

I eventually uninstalled FW using Revo Uninstaller. I also went through the registry and deleted any entries for FrostWire or LimeWire. Rebooted my computer and then reinstalled as administrator. That seemed to work.