Firefox is not a particularly customer centric organization. They don't respond to requests, don't seem to follow up on suggestions and don't seem to watch their own fora. Nevertheless this is still better then using Google stuff and being sold in th...
It is definitely related to the ClearURLs extension, I disabled it as well and problem solved. Easy to reproduced. Enabled a bunch of other extensions to try it out, it only happens with ClearURLs.
