If you are experiencing difficulty in sending files or starting an audio conversation, you may be behind a firewall or may be using Internet-sharing software or hardware, a system also known as ICS/NAT. To learn more, see "ICS/NAT Issues" on the MSN Messenger Known Issues
page. If you are behind a firewall, contact your Network Administrator and request that they consult MSN Messenger Help topic Guide for Network Administrators
(found in the MSN Messenger Help
menu). The basic functions of MSN Messenger should be unaffected because ICS/NAT issues affect only certain features.
Also, make sure your contact is not behind a firewall or ICS/NAT. If possible, try this with more than one contact to verify the problem is not with just one contact.
If you are still experiencing difficulty sending files or starting audio conversations after this, please contact MSN Messenger Support here