PM envelope doesn't change color for new PM's

Hello

 

I have noticed now for a couple of days that sometimes the PM envelope doesn't turn yellow or orange when I have a new pm.  Sometimes it does work ok though. I don't have my preference set to receive an email for pm's. As a result, it's hard to know if I do have a new pm unless I just go there and check any way.

 

I'm using XP Pro Sp 3, IE 7 and all fully patched.