bug#5180: 23.1.90; Secondary selection and M-w

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug.  If you can, give
a recipe starting from `emacs -Q':

If often use mouse to select a piece of text and then hit M-w to copy
it. However, this is frequently hijacked by mouse-drag-secondary.

To reproduce:
1. Drag the mouse to select some text
2. Stop dragging and (after a short delay) hit the Meta (as in M-w) key

The region will be turned into a secondary selection defeating the
effect of M-w, for example.

I have found this annoying and I wonder how to fix it without disabling
all secondary selection bindings.

Thank you.

Leo

with GNU Emacs 23.1.90.1 (i386-apple-darwin9.8.0, NS
apple-appkit-949.54) of 2009-12-09 on victoria.local