In Microsoft Office Communicator 2007 R2, if you send hyperlinks in an instant message as text instead of as true hyperlinks, the hyperlinks are converted to lowercase.
For example, if you send the hyperlink http://example.com/GREATSITE as text, the recipient receives http://exmaple.com/greatsite as a true hyperlink. However, if the Web site that connects to the hyperlink is hosted on a server where Web requests are case-sensitive, you cannot access the desired Web site. Therefore, if the recipient clicks the hyperlink, the Web page is not displayed.
This problem occurs because the way that Office Communicator 2007 R2 creates and handles XML tags depends on the way that you enter a hyperlink.
To resolve this issue, apply the following update:
972884 Description of the update for Communicator 2007 R2: Oct 2009
To work around this issue, send hyperlinks in instant messages as true hyperlinks.