Try run AFX in Administrator mode, make sure your composition's name doesn't include any special characters and don't forget to add exceptions to your firewall.
Thank you for providing this advice. However I must point out that gifsquid does not phone home or use the internet in any way.
I know that, yet convert.exe was blocked by default in Comodo Firewall, Tiny Wall and some antivirus software. That was causing my export problems.
Tried this and still had the same problem.
