Running vista, which sux too... have been using ff WITHOUT probs since beginning, however latest version (4) will not open...icon spins and then stops and nothing. If I try to uninstall get message saying I need to close firefox...even though its not open. When I try to install last working (great working) version, it gives the same message to close firefox when its not open. Hopefully you guys will be be fixing issues real soon b4 u will loose a lot of users... just in case u r not aware of all the issues, read your problems sections. For the first time since started using ff and blowing ie off all together, I am very disappointed in your product.