Yes, we had a case  two week ago. The user was locked every day. We found he was logon another computer using remote desktop. You may try

resource kitsCConnect.exe - Monitor user connections to servers and which system they are logging in ... Show how many users are logged on to a domain controller (DC). ...
     www.chicagotech.net/resourcekits.htm  

Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net 
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com 
 HI,
 I support a development environment wherre the users access multiple pc's
 through VPN, Remote Desktop, PC Anywhere, etc. I believe that user's accounts
 are being locked up because they fail to log off every pc they have logged
 into, and their passwords become unsynchronized. Has anyone else seen this
 problem?

 Also, does anyone know of any utility I can use to find out which pc's users
 are logged into on the network?