I've been battling a very annoying issue with CS3 on Leopard. It seems that text entry into some tools fields (crop tool specifically) has big issues. I went to the Adobe forums today to see if there is a work around and thank goodness there is!
http://www.adobeforums.com/webx/.3c054baf/2
If you hover your mouse on the words "width", "length", or "resolution" in the tool bar, you will see the pointer change to a finger with arrow left and right. This is now a slider that will allow you to change the values without typing. Before this discovery, the only way to fix the issue was to save your file, quit, then restart Photoshop. Made me very cranky when post-processing images.
I think Adobe is pointing the finger at Apple on this one... At least this work around will save me time!
Have fun!