Hello!
We believe that this is the problem with Antivirus blocking MF Pro from working properly.
We are currently testing a fix, which everybody can download and try:
MarketFeeder Pro 8.6.1.3Some users have already confirmed this helped them solve the problems with Market Locator critical error, Formula Builder error and Settings error (all of them blocked by the Microsoft Security Essentials or other antivirus software with false positive virus alerts).
Please post here if this helped you too (or if it didn't).