Unable to copy/paste

[manolo]

Binary package hint: firefox-3.5

Sometimes it happens that selecting phrases from a web page turns the selection bar grey (meaning "unabled" in some manner) after clicking on it with the right mouse button. Actually the bar turns grey not immediately after pressing the right mouse button. in fact, it remains brown (that is "active" in some manner) as long as I move the mouse pointer on the related menu window in order to select the "copy" option: in this moment it turns grey and pressing "copy" doesn't copy the selected phrase but possibly pasts the last stuff previously and correctly copied.

The problem presents randomly and not with a specific web page, so I have no idea on how to reproduce it.

Any suggestion, please?
Thanks.

ProblemType: Bug
Architecture: i386
CheckboxSubmission: fd2ed44d5b03d6e55ebd91dcef8ce907
CheckboxSystem: 2954e74ba17fb0e37fc942cd1d9fab4e
Date: Wed Mar 31 17:34:58 2010
DistroRelease: Ubuntu 9.10
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
Package: firefox-3.5 3.5.8+build1+nobinonly-0ubuntu0.9.10.1
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-20.58-generic
SourcePackage: firefox-3.5
Uname: Linux 2.6.31-20-generic i686