>Sorry Nadia, cannot duplicate, I don't have a paying account in UT and this function is restricted for us.

Try it with creating a new thread, choose "Create a new thread to a member" (the second tab at the top of the message), when click on magnifying glasses icon. This should bring the same dialog and it doesn't work for me.

I think I may have accidentally clicked on something today when I was re-setting my default e-mail client using about:config page.

Anyway, if you can confirm it works OK for you (and I believe it worked for me too), then I need to investigate the problem.