User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0.2) Gecko/20100101 Firefox/10.0.2 Build ID: 20120215223356 Steps to reproduce: Typed text using Helvetica (default). After spontaneous change, selected entire body and clicked on Helvetica. Text all changed to Courier. Clicked on Courier, text all changed to Helvetica Actual results: Text spontaneously changed to Courier after a line or two. After click on Helvetica, text all changed to Courier. Clicked on Courier, text all changed to Helvetica Expected results: Text should have remained Helvetica, and when I selected a given font, selected text should all have changed to that font. Instead, it appears that the two are reversed..
(In reply to Pete Smith from comment #0) Are you composing messages in HTML or text?
I am sending messages in "both HTML and text". So far as I know, T'bird does not offer an explicit option of *composing* in HTML or text, but it appears to me, from the facility with which the displayed text changes fonts on the fly, that I must be composing in HTML
(In reply to Hashem Masoud from comment #3) > (In reply to Pete Smith from comment #2) > Probably similar to bug 250539. Indeed.