Some problems with that version in FireFox. After pasting in lengthy text, I start to type at the top and FireFox hangs and we get this error message:

 

Warning: unresponsive script

 

A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete: [Stop script][Continue]

 

When I click [Continue] it continues to hang for some time then releases. If I then type a few more letters, it hangs again and displays the error message again.

 

If I click [Stop script] same thing. I type a few more letters and it hangs...