"This operation has been cancelled due to restrictions in effect on this computer. Please contact your system administrator."

If you are getting this message when you try to use a hyperlink in Outlook or other MS Office, it is not a security issue, but an extension issue that was the result of a recent Vista update. To solve the problem:

Click Start/Default Programs: 

Click Set Program Access and Computer Defaults => Custom.

Select IE and Outlook and restart IE and Outlook. The links should work...