Mouse over doesn't work in Windows Rated 3 out of 5 stars

The mouse over function is very handy and works fine in Mac. However it doesn't work in my two Win7 PCs. Any settings I should check?

This review is for a previous version of the add-on (0.3.0.1-signed). 

Unfortunately I haven't got a Windows7 machine to test with. What version of Firefox are you using? Do any other extension's custom tooltips work?