As of this writing some Java-based apps still don't work well with OS X 1.5.x (Leopard) Spaces feature. Specifically, if you are in a different space than where the IDEA window currently resides, command-tabbing to IDEA won't switch you to IDEA's space. Another side effect is that clicking the IDEA icon in the doc wouldn't bring you to the correct space either.
I noticed awhile back that if you had two idea projects open in the same space then the problem was solved, Spaces would then work properly with IDEA. The problem was the pain in the butt factor of having a blank 2nd project open (extra memory and thread resources).
I noticed that having any of IDEA's modal dialog windows open (like preferences) also solved the problem. Today it finally dawned on me to try IDEA's help window and, yes, it worked!
Solution
Simply open up the IDEA help window and put it behind your working project window. It won't work if you minimize the help window - it has to be open. Works great and doesn't suck resources.
Another solution that works, if you don't mind it, is to float one of the windows (e.g. the debug window). This works well if you have two monitors. Simply click the "float" button on any of the windows and move it out of the way.
Let me know if you have any other ideas or if there is a permanent solution available.
