NIS 09 Disables Firefox Extensions & Themes

I just recently installed Norton Internet Security 2009 on my computer. However since then Firefox has been unable to run any themes or extensions. It says that they are there & when I use them they make out they are woring however when I restart firefox to use my themes they are not there & I am left with the basic theme. Also when I try to install a theme or extension it brings up this error message:

 

"Firefox could not install the file at

addons.mozilla.org

 

because: Unexpected installation error
Review the Error Console log for more details.
-203 ."

 

Please help.

 

Message Edited by TB_Boy on 04-05-2009 12:26 PM
[edit: Please refrain from posting download links per the Participation Guidelines and Terms of Service.]
Message Edited by shannons on 04-05-2009 02:04 PM