when running CDE on Ubuntu 12.04 x86_64, right-clicking on any icon on the panel will show the contents of the menu with some duplicated, and a number of spurious ones labeled "action_button." Clicking on any of the "action_button" entries will cause dtwm to disappear. issue has not occurred for me on Ubuntu 12.04 or 13.04 for i386.
steps to reproduce:
1) on a clean install of 12.04 x86-64, download/build/install CDE exactly as described on the Linux Build Wiki (pulling source from git.)
2) right click on any icon in the front panel, you should see something like the attached screengrab.
3) click on any of the "action_button" entries. dtwm will disappear, leaving open windows floating in limbo.