Sip phone or switch blocking windows messenger service

When a sip phone is in-line with a pc, the pc’s windows messenger service does not receive the network signals.

I have tested three sip phones: snom, polycom and grandstream, inline with three separate users pc’s.

So either the 10/100 switch is not passing it though, or more likely, the sip phone is intercepting the communication.

The client relies on the messenger service for internal applications.

At some point I’ll add separate phone/pc rj45 jacks, but not for a little while. Any thoughts on how to get messenger service to work alongside a sip phone?