OK, I did send it now to the developer by email, I truly hope he can help. I wonder how people can use the software if it duplicates their sync every time they do it. I could not not find anything unique about the way I worked with this sync solution.
It's more likely something unique about your computer. Most people seem to get along fine once they get past the initial setup of the app. It's just a matter of getting it going in the first place
FYI, the Firefox issue is isolated to the most recent version. Toodledo is working on optimizing that. IE works, but you can also roll FF back to a previous version (the latest one is somewhat buggy IMO anyway).