Try doing the following:
Open up Internet Explorer
Select the Tools Tab
Click on Internet Options
Select the Advanced Tab
Scroll down until you see a section titled Java (Sun), an icon that looks like a purple cup with steam coming out of it will be next to the section.
Make sure there is a check in the box underneath the it (it'll say something like Use Java 2 v ....).
I don't know if it'll fix you're problem, but it's something I thought of. Also, make sure you have the latest version of Java installed (version 5 Update 6). To do this, perform the following steps:
Open up your Control Panel
Launch the Add/Remove Programs Application
Search for J2SE Runtime Environment 5 Update 6. If you don't have it or have a different version, please go to http://www.java.com/en/
and download the latest version.