I had no vertical scroll in Excel 2010 and IE 8 (using Office 2010, Windows XP-SP3 and a wired Logitech optical mouse), but it worked OK in Outlook, Word, etc. I tried to toggle on/off the zoom option in Excel (and the zoom worked) but scrolling didn't return. I also tried many of the other solutions out there that I could, but my options on the Control Panel, 'Mouse' applet's 'Wheel' tab were very limited.
Finally, I decided to download and install the most recent version of Microsoft's IntelliPoint software (v8.2, basic optical version for USB & PS/2), even though I was using a Logitech mouse:
Other options can be found here:
I figured that since my Logitech mouse didn't need any special software to run (according to Logitech), that updating this software might help. I could always uninstall it later if it didn't help. After installing the software and rebooting, my problems have been solved.
The Control Panel applet correctly says it can't detect a Microsoft mouse, but it added various vertical scroll options to the 'Wheel' menu and everything works great for me now (with default options selected). I don't need to reassign button functions, etc. so that is no loss, I'd much rather have a functioning vertical scroll. If full functions are important to you, Microsoft recommends downloading/installing a version prior to Intellipoint v8.0.
I hope this helps!