Outlook, Hotmail, Messenger, and XP Service Pack 2

[J]

I've been using Windows Messenger for years, and have
grown very accustomed to the popup window that sprouts
when I receive a new email in my Hotmail account.

Since installing Windows XP Service Pack 2, the popup no
longer appears. Also, (and I know this is related) when
I right-click on the Messenger icon and select "My E-mail
Inbox", it opens Outlook (which I've also used for years
for my corporate email), instead of Hotmail in Internet
Explorer.

Now, I'm a well-educated, technically savvy software
engineer, but this problem's got me whining and crying
like a noob. Somebody, anybody, please tell me how to
fix this!

J