shell command completion problem

[Markus Rost]

At the command line in buffer *shell* (opened with M-x shell) type
some letter, say `p' and then hit TAB (comint-dynamic-complete).
The buffer *Completions* pops up.  Fine.

Suppose you want to search in this buffer.  So you might type C-x o
(other-window) to switch to the window showing buffer *Completions*.
But that window will disappear immediately.

This happens also when clicking with mouse 1 in that window.

Sometimes but not always I get here error messages like:

mouse-drag-region: Wrong type argument: window-live-p, #<window 7>
mouse-minibuffer-check: Wrong type argument: window-live-p, #<window 7>