Outlook Express problem with HTML Mime Mail Class

[sstaubin01]

I'm using Richards Heyes's HTML Mime Mail Class (send method) to send email with imbedded images, links and variables (variables are from MySql tables). The Email is created and sent fine but if I try to open it in Outlook Express, Outlook Express goes into a 'not responding' status. The same email sent to a hotmail account and opened in hotmail's mail client opens fine. Any ideas why Outlook Express gets fried? The site is in development and not hosted. I'm using PHP, MySql and Apache for win32. Pages are served with Apache at localhost (127.0.0.1).

[sstaubin01]

Does this make any sense? When I send the email I have had Outlook Express open, but if I send the mail when Outlook Express is closed the mail opens without locking up Outlook Express. I've just noticed this and haven't tried it alot to verify but can anyone explain why this might be the problem?