popup-menu erases header on w32

[Lennart Borgman]

A popup menu has a header (in bold face). This sometimes gets erased, at 
least on w32. To show this eval the function below:

 (defun my-popup-menu-error()
   (interactive)
   (popup-menu '("Test 'repop'"
                 ["Pop me up again" my-popup-menu])
               (list '(100 100) (selected-window))))


Then call the function

  M-x my-popup-menu-error RET

Now use the up and down arrow keys a number of times. Everything should 
be OK so far.

Now choose the entry "Pop me up again". Use the up and down arrow keys a 
number of time again. At least for me this erases the header.

I have tested this only on w32 and would be glad for a test on other 
platforms.

My current Emacs is GNU Emacs 22.0.50.1 (i386-mingw-nt5.0.2195) of 
2006-05-01.