Vista Tutorial - opening multiple attachments

Have Vista Home Prem w/SP1, using Windows Mail.
Use Webroot Desktop Firewall, and Spysweeper with Antivirus - both
applications set to allow traffic.
For business, I regularly recieve an email with one pdf and three MS Word
files.
I can open any one file, and then must close the Mail app and reopen for
each attachment.
This was not always the case.
Can't find this exact problem in recent discussions.
Any help appreciated.
Thanks,
Bill K