folders getting new mail from message filters do not show new mail

i have a bunch of folders with filters sorting incoming mail into these folders.

the folders are not showing that there is new mail in them until i click on each one and it "builds file summary"

I think the problem has to do with switching from vista/win7 and xp. I first started using on xp and all is fine, then when i started switching from xp and vista I first noticed it happening. and now that i switch from win7 and xp I see it all the time.

has this been noticed by anyone else? is there a fix?

i use an xp machine with portable thunderbird version 2.0.0.21 (20090302) to download mail, then i use a win7 machine at a later time to read.

welp!!!!!!!!!!

/s