Pitty...
If you look in the given folders, and the creation date for directories and files.. don't one or two stick out?
I can have a go to replicate this.. but that probably won't be before Monday.
edit: I just realised you can also have a look in the GNOME config editor:
Start gconf-editor in a terminal or using the menu's more applications, then open the keys Desktop > Gnome > Url-handlers
Maybe you can find the handler thats causing the error by having a look through the handler configurations.