I haven't seen that particular message, but a couple basic troubleshooting tips:
1. Make sure your FTM is up to date - click "Family Tree Maker 2" menu, then "Check for Updates"
2. Make sure OS X and Safari are up to date - click Apple menu, then "Software Updates"
3. Restart the computer
4. Web records in FTM use Safari (regardless of what other browsers you have on your system) so quit FTM, open Safari, click on "Safari" menu, select "Reset Safari", and make sure that "Remove all website data" is checked (other boxes can be checked or unchecked as you wish), then click [Reset].