Have you tried cleaning out all your temporary files and cookies?

In tools, on the General tab, click on clear cookies and clear files, clear your history too, just for good measure. Then restart your computer. If that doesn't work, try a disk clean - Start, Programs, Accessories, System Tools, Disk Cleanup. Make sure all the little boxes have check marks. If you have never done this, it might take awhile. When it's done, reboot and see what happens.