User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US) AppleWebKit/533.2 (KHTML, like Gecko) Chrome/5.0.342.7 Safari/533.2 Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 Repeatable with these steps: 1. A popular application this problem occurs with is google chrome. Have google chrome browser running 2. View a web site, any site 3. Click the URL at the top, highlight it and press CTRL-C to copy it 4. Open up a thunderbird new email message 5. Type something in the message 6. Now press CTRL-V to paste the URL 7. Notice that having done that, the text cursor jumps to the very start of the email 8. Also notice that if you press CTRL-Z or choose Edit/Undo, nothing happens. The paste and all the previous changes cannot be undone. Reproducible: Always

Have you tried safe mode? (see https://support.mozillamessaging.com/en-US/kb/Safe+Mode for more information)

Running in safe mode makes no difference to the issue reported in this bug. I can see however when running in safe mode, when choosing Tools/Add-ons that it says "All add-ons have been disabled by safe mode."

Is the problem Google Chrome specific, or does it happen with pasting from some other app ? This does not occur if you past a url from Firefox, so we need to see what actual html is being added in your use case. If you could supply an eml file for analysis, that would be great. Or...At the point where the cursor jumps to the start..use File>>>save as (html) then provide that file as an attachment here. Oh, and BTW, are you composing in plaintext, or html mode.

This may be google chrome specific, but there are other pasting problems with pasting from various applications, for example, thunderbird consistently bombs if you paste anything from the netbeans IDE into a message. I have submitted crash reports on that matter with wording "pasting any text from netbeans ide crashes thunderbird". I attach a save of the message just after pasting. Options/Format has auto-detect mode set.

Duplicate of/related to Bug 261392 comment 8 or bug 532379 -> Core bug 493189?