What do these error messages mean?
An unexpected token in TDS indicates a bad network packet was sent to the TCP Port Sybase is listening to.  

This indicates one of two things:


an intermittent network connectivity problem where TCP TDS packets are being corrupted
you have some process attempting to connect to the Sybase instance without using TDS.  


I've seen #2 happen with security scanning processes that are looking for open ports.

From your symptoms it sounds like a network connectivity issue.  Since the Sybase Anywhere server is not on the same network segment as your client machine, I'd tend to think the client needs to gracefully handle connectivity problems.