Once you have it open, you can literally leave it up and watch the Status of the Firefox Application switch back and forth between 'Running' and 'Not Responding' as this issue comes and goes. Even pressing CTRL-ALT-DEL does not produce the Task Manager immediately. When this happens the entire machine is slowed to less than a snail's pace. Even plain with no other sites open and nothing logged in can trigger this.
Stopping the script does not solve the problem in all cases, and as soon as one goes to another page or site it begins all over again. Suddenly, last night and today it has become unusable due to scripts hanging the system for several minutes at a time and eventually displaying an error message popup about it which gives me the option to Continue, Debug, or Stop the script. xesr Portable on my machine for over a year now.
