Compiler hangup

Hi, I am currenly using IDEA 4.0.3 on a windows XP box with J2SE SDK 1.4.2_04. This works fine for most things but I have a GUI project which hangs every time during project build. I get the Compiler Progress box which hangs at "Loading Classes". If I cancel, the run and build buttons are useless, I have to close and reopen the project again. With the same versions on a Linux box no problems ... maybe I should do the sensible thing and stick with Linux!!

Any thoughts?

/Dominic