[Greasemonkey] fails in Firefox/Ubuntu

[larytet.15770275 at bloglines.com]

when i try to add JS first time (menu Tools/New User Script) firefox opens
dialog and let to choose JS file. after i click Ok firefox does not respond
with any additional messages. The script does not appear in the Manage User
Scripts. When i try to add the script file again i see the following error
on JS console

XML Parsing Error: no element found
Location: jar:resource:///chrome/toolkit.jar!/content/mozapps/update/updates.xml

Line Number 1, Column 1:

Firefox does not open any dialogs on the consequent
attempts to add user scripts.

I tried both HelloWorld from the tutorial
and Butler. 

i am running Firefox Mozilla/5.0 (X11; U; Linux i686; en-US;
rv:1.7.10) Gecko/20050721 Firefox/1.0.6 (Ubuntu package 1.0.6)


thank
you