When click Hyperlink in Outlook 2007 error message pops up

I am a regular Firefox user and loving it. A few days ago I upgraded to Firefox 4 version, to enjoy the new features.
But I found some critical options and also I am having problems with some of the add-ons. So, I reinstalled the previous version again. But after that I can’t open some of the hyperlinks in Outlook 2007.
If I click on the hyperlink of a message, the error message pops up and suggest contacting with the administrator for the solution.

Microsoft Office Outlook
This operation has been canceled due to restrictions in effect on this computer. Please contact your system administrator.
But I am the administrator of my PC.
I tried to access those messages by creating a new user with administrative power but an error message still comes up.
Do you have any suggestion?
