Send message windows doesn't close after sending attached PDF from Acrobat

Question

I have several forms that I have created in Acrobat 9 Pro. These forms have a button set to submit to an email address. After filling out the form, and clicking on the submit button some, but not all, of users with Outlook 2007 are having a problem with the send message window not closing after sending the email.
When they click the button the email is created with the form as an attachment. When they click the send button in the send message window the message goes into the outbox, and then gets sent no problems. But the send message window never closes after sending the message. So my users think the message never got sent.
The computers that I am seeing this on all run XP, have Outlook 2007, and use Acrobat Standard 8. On some computers it works just fine, and on others it has the problem. It must be a setting somewhere but I can not figure it out.
Closing the window by clicking on the "X" is no problem, but many of my users are pretty new to computers know very little about them. So something like this causes them a lot of problems.
Any suggestions?
Trudy

Answer 1

My apologies, when I said "instance" I meant window.
I also just realized the new window and then closing behavior only happens when the iTunes link clicked is in an email in Mail (presumably, this would also happen in other desktop email clients). When an iTunes link in Safari is clicked, the "iTunes loading" white page appears for a moment and then Safari navigates back to the page with the link. However, that isn't working properly, either. The white page continues to "load" indefinitely and never returns to the previous page.
Here is a link:
http://www.imogenheap.com/buy/