sometimes putty screen gets garbled (not updated properly) when text is scrolling

I have had this issue since a long time ago (I believe it was from Ubuntu 8.10, but I am not sure), then it finally went away in 9.10 and 10.04 and 10.10, and it seems it is back in 11.04. (the computer is always the same, a Dell Precision with a Nvidia graphics card)

Sometimes, when using Putty, the screen does not update properly. Tipically some rows of text are not displayed properly, and the old content remains where there should now be no text (black background) or where there should be new text instead of the old one. Sometimes new text is not drawn where it should be, and parts of lines or entire lines remain empty.

This happens a lot more frequently while scrolling a screen full of text, and happens more frequently when using putty at full screen (that means a lot more text to scroll than the classic 80 rows x 25 columns).

It seems to me that somehow screen updates do not work properly while scrolling fast and when there is a lot of text to scroll.

If I move through "old" text using the scrollbar, however, it works. It seems that only scrolling originated from the remote host actually writing to the screen causes the issue.

 I also suspect that this has something to do with X server, video driver or Compiz settings, more than with a specific version of Putty, but I am not sure.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: putty 0.60+2010-12-08-1
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Wed Jul 6 15:16:34 2011
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
ProcEnviron:
 LANGUAGE=en_GB:en
 LANG=it_IT.utf8
 LC_MESSAGES=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: putty
UpgradeStatus: Upgraded to natty on 2011-06-22 (13 days ago)