It seems that this problem only occurs when there are other items in the Startup Items folder which are launched after PPPop2. Still looking for the cause of this problem. This should force PPPop to launch last. PPPop 2.0.4 4. Double-clicking on one of these windows, or even clicking in quick succession, may cause the Mac to freeze.
Single clicks are no problem.
More direct attempts at a fix have not been successful. The cause is yet to be determined.