I am only responding since I use Outlook Web Access to retrieve email from my school email account. I know that public institutions are often way behind the consumer market when it comes to software.

Perhaps the domain that you are trying to reply from is not capable of handling the Vista format. You may need to contact your network administrators. I know this was an issue initially when XP launched and our school district was strictly in the 2000 format. It took some time for IT to resolve this issue.

The problem may not be with you, but instead, with them. It's worth a shot, especially since Vista just launched such a short time ago.

Mary :)