Some users that upgraded to Internet Explorer 8 experience issues with tabs not working properly or taking a very long time to load. It seems for most users the issue can be attributed to a problem with actxprxy.dll not installing properly during the upgrade. If you have a similar problem with IE8, fixing the issue is as simple as a running one command.
Just open up an administrative level command prompt and type in regsvr32 actxprxy.dll and hit Enter. Reboot your computer and your tab issue should be resolved.