Mail App password frustration

[good-dog at northshore.net]

Folks;

My girlfriend's Cube, running the latest Jaguar, has a consistent 
difficulty with the Mail App we can't seem to fix.

No matter how many times we write in her password and click the little 
box to remember said password, each and every time she opens her mail, 
and sometimes during a lengthy email session where her email is checked 
automatically, the dialog box asking for the password keeps coming on, 
as if we never, ever, ever, ever checked the little box.

Anybody have any ideas?

Thanks.

Mark