Ubiquity do not start

I don't know perhaps i am doing something wrong, but it is impossible for me to start ubiquity, i have tried several times desinstall reinstall Ubiquity, it installs the addon, and it is shown in the addons, but if i press ctrl space, nothing happens. I use ubiquity not that often, but i know that it had shown me purpose to use ubiquity commands in the past, and i also used ubiquity in the past, but now its impossible for me to use ubiquity, don't know perhaps it is because i have addblockplus installed, or perhaps i should deinstall and reinstall firefox, perhaps i have tried to often to install and reinstall ubiquity and now, there is something not working. I don't know perhaps somebody had the same problem, and can help me, or perhaps this is also a failure that i can report to the community.
I am using a Windows 7, Firefox 3.5.5 and my only addon alongside ubiquity is Addblock plus.

Ok, then thank you very much for help

Cef