i too have had the same problem however i use internet explorer not firefox
..i think it is a result of program incompatibility .i could not open any
thing long enough to delete the offending program so i had to try to do a
system restore from startup but this failed because norton will not allow you
to do this (are you using norton) so you have to disable norton before any
restore can take place . i have since contacted symantec about this problem
and i have given you their responce below in case it is of any use to you
--
martybThank you for contacting Symantec Online Technical Support.
I understand from your message that when you try to perform a system
restore, you need to disable Norton first. You wish to know if there is a
major issue where you cannot start your computer in normal mode how you would
be able to perform a system restore.
Martin, please be informed that System restore can modify the files of the
Norton program. For example, when you perform a system restore, the virus
definitions files are reverted back to a previous date. Norton program
includes a feature called Symantec resource protection which prevents the
modification of the Norton program files. Hence you would not be able to
perform a system restore without disabling the Norton program.
In case, where there are major issues , where you cannot start your computer
in normal mode, you can perform a restoration by booting in safe mode. To do
this, please follow the steps given below.
1. Restart your computer, and then press F8 during the initial startup to
start your computer in Safe Mode or Safe Mode with a command prompt.
2. Log on to your computer with an administrator account or with an account
that has administrator credentials.
3. In Safe Mode type or paste the following command in the Start - Run box
then press Enter. In Safe Mode Command Prompt type the following command then
press ENTER.
%systemroot%\system32\restore\rstrui.exe
4. Follow the instructions that appear on the screen to restore your
computer to an earlier state, or undo the last restore if available.
The following weblink has more information in this regard.
http://support.microsoft.com/?kbid=315222&sd=RMVP