Has anyone experienced sync issues when using Medusa with UGPS?

We'd love to dig into this further and fix your issue... 

Just to clarify, you are using a cable to connect the AUX port on the 450m (RJ-45) to the UGPS port (RJ-11), correct?  Is this standard Cat5e cable?  How long is the cable?

I assume you followed the pin configuration as noted here.

Is this the only thing connected to the UGPS?