When I launch PT4 the welcome window pops up with its widgets dead. It blocks almost the entire PT4 GUI and thus prevents access to most of the PT4 controls.  Any subsequent windows or drop down menus are also zombies and clutter the desktop.  Meanwhile the piano works fine – I just can't  change anything.  Clicking the exit button shuts down PT4 properly and returns the desktop to normal.

Kubuntu 8.04 is a bit dated and may be the source of the problem. My desktop PC is currently running Linux Mint 12 (based on Ubuntu 12.04, the latest stable version).  I plan to install that OS on the laptop to see if that makes PT4  happy.  Will post any new developments.

In the meantime PT3 still runs fine so that I am not actually adrift.