I am getting headers showing two identical From: header lines, and in the area where you manage the headers to display, that too is showing two From: header lines, please see screen shot linked. Unticking one of the two From: boxes works until a screen refresh, the both From: headers are back. I can see the extra From: header in Options : Preferences : Message Headers, but the option to delete either of the two is greyed out.  Thanks.TB1 is V 5.8.8 but did it with an earlier 5.8 version too.

http://www.gatesgarth.com/headers.jpg