mail won't save message as plain text

I recently upgraded from an old macbook pro (3,1 running 10.4.11) to a new one (5,1 running 10.5.7). The problem is, I can't email (mail 3.6) as plain text. I can save the exact same message as text on my old mac (mail 2.1.3).

The mail is saved as rich text, even though I select the (save as plain text) option. The fact that I can save the same message as plain text on my old mac suggests that there is either some option I have set elsewhere that is overriding the 'save' option, or there is a serious bug in this version.

A would greatly appreciate any advice, as this is critical for my work.

-W

 

correction

Typo in my original post:

"The problem is, I can't email" -> "The problem is, I can't save mail"

--M