I use Windows XP and just upgraded to Firefox v2.0 and Yahoo Mail. Often, when I try to forward an e-mail (inline text with picture) the picture is deleted and I get some text in it's place. The text is always the same: 

When I display full headers I've noticed that the pictures that don't display have the following information:

Mime-Version: 1.0 (Apple Message framework v752.2)
X-Priority: 3 (Normal)
Content-Type: multipart/alternative; boundary=Apple-Mail-9—49715394...

Pictures that do display do NOT have the Apple Message framework information in the header.

Has anyone else had this problem? How have you resolved it? Whatever information you can provide will be appreciated.

Those are probably being sent to you by a Mac user. If that's the case, they will have to make the attachments Windows friendly. See article here:

Apple Mail Help

I just installed Firefox 1.5 two days ago (new user) only to learn today that Firefox 2.0 is out. Installed it and it's running fine. I am also on a WinXP machine and use Yahoo Mail. I just got an email from a MAC user and her emails are coming through just fine as they always do. Firefox 2.0 isn't causing me any Yahoo mail problems that I can see, but she didn't have a picture attached to confirm that comment. Maybe something in the MAC user's email configuration is causing this for you? or the picture format (extension) is wrong for a Windows system? Sorry I have no other thoughts on this.