Every once in a while I run in to a small issue with Firefox not loading correctly when i save my session.  It seems to happen when I have multiple tabs open that have lots of JavaScript running in them.  In my case I couldn't access the GUI like in the method shown here or here.  I had to manually delete the session file in my Firefox profile. Here's how to do it.

• From My Computer navigate to C:\Documents and Settings and click on the folder that is named your windows xp user name Or hold the windows key and press the R key.  I'll notice that the Run dialog pops up, now type in %appdata%
• Find the folder named Mozilla
• Click on the folder named Firefox
• Click on the folder named Profiles
• You should be in \Documents and Settings\YOURUSERNAMAE\Application Data\Mozilla\Firefox\Profiles\
• In this folder there might be more than once folder.  Select the one that has the newest date modified.  This should be your profile
• Find the file named sessionstore.js and delete it.