Do you by any chance have Downloadhelper installed? I had a similar problem with an older version of downloadhelper. But I'm using 3.6.3 as well and the latest version of downloadhelper and it works fine.
Yes i reinstalled it serveal times
also at a point i did have a download manager but i don't have it anymore
Here are a list of the following plugins i have installed
Microsoft Office 2007 plugin
Google Update
Shockwave Flash 10.0.r45
Silverlight 4 plugin
WGA plugin
Windows Live Photo Gallery