The two things to check would be going to the Pref Pane for Keyboard and Mouse, selecting the Shortcuts tab, and looking through the list to see if there's a command-T in there anywhere; that might override the key command in other apps if there is. (I see a command-option-T in my list, but no straight command-T.)
The other would be to ask if you installed any system additions/hacks recently that might have created a systemwide command-T shortcut to do something, that is then overriding the regular behavior.
Obviously it's not the keyboard itself, since you can type it...