A part of the setup process it checks to ensure that the form is being completed by a person and not automatically by a computer/robot by asking for 2 words to be entered (a captcha). You should get a picture showing 2 words, you need to type those 2 words, if you enter the words incorrectly you get that error message.

If you do not see that captcha then you can check:

• http://kb.mozillazine.org/Images_or_animations_do_not_load

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your problem.

See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

Thanks for the reply. I only get an empty pop-up box not the picture with two words. on top of the box it says: please confirm....

How can I make Firefox to show the captcha image?

Thanks for your help. I tried safe mode and the other suggestions in the trouble shooting sites. No success. In the end I had to restore FireFox because I could not get out of safe mode. I have to abandon Sync and look for another synchronizer.