Cursor movement key repeat painfully slow when text selected

[Skip Montanaro]

I work in an environment where my desktop computer runs Win 7 and I
use PuTTY to connect to the Linux hosts on which I actually do
software development. When I get to a dev host, I run a GUI instance
of Emacs. It comes up in its own X window. Everything's fine until I
select some text. Emacs helpfully changes the background to indicate
the region between point and mark which is currently selected. If I
hold down any cursor movement keys (arrows, C-p, C-n, etc) cursor
movement grinds to a halt. I suspect the basic problem is that the
Xming X11 server is a dog.

Is there some way to make the highlighting of the selected region
lighter weight (maybe just highlight mark and point or just mark) so
less work needs to be done by the server to keep the display updated?
Unfortunately, PuTTY and Xming are a given. I have no ability to
replace them with anything more efficient.

Thx,

Skip Montanaro