Q: My mouse does not scroll up, but it does scroll down

Probably needs a clean.

How to really clean your Mighty Mouse (with caution!):

http://support.apple.com/kb/HT3226?viewlocale=en_US

and:

http://web.mac.com/karelgil/iWeb/MacWebSite/MightyMEng.html

http://www.linklink.co.uk/apple-computers/cleaning-inside-and-dismantling-the-ap ple-mighty-mouse/

You didn't mention what mouse you have. They're not all the same, some wear out faster. I'm using a Kensington Optical Elite which is inexpensive, programmable, and reliable. You can get one on Amazon.

Good point!

I long ago gave up on Apple rodents and have for 3 years used a cheap Logitech B110 mouse, also from Amazon. Cost less than £10 and has never needed a clean!

Try this trick. It worked for me.