Windows 7 - Middle mouse click no longer opens or closes new tabs in ie or firefox

All of a sudden I can no longer open or close new tabs using the middle mouse click (clicking the scroll wheel) it doesn work in ie or in firefox. Also seems like it doesn't work on the desktop or any other application. I have'nt installed new updates or new programs, I don't have any "mouse software" like intellipoint. This affects both my wireless keyboard with built in trackball and a serperate wireless scrollmouse. The only think I can think of is that a few days ago I changed the the speed of my cursor.. of course this shouldn't have affected anything else.... but it is really annoying as I mostly use my computer for web browsing and always open links in new tabs... Please help!

What make AND model of mouse do you have?

its a wireless keyboard with a trackball built in; actually it's fixed... was a dirty switch under the scroll wheel. took apart keyboard and cleaned, thanks anyway...