This is what I suspect is happening:
When the JTAPI client sends the connect request to AE Services, it starts a timer. It expects to receive some indication that the call is making progress within this time. Usually, the far-end network returns a Ringing/Alerting event almost immediately, which is sent back to the JTAPI client and it stops the timer.
Some networks do not send Ringing events, so the first event that the JTAPI Client receives is an Answered/Established event. This will not be generated until the call is answered.
If the call is not answered or the far-end user takes too long to answer, JTAPI Client will timeout and generate this error.
The length of the timer is controlled by the callCompletionTimeout parameter in your TSAPI.PRO file. You can change this to be longer.
There is more information on JTAPI properties in the JTAPI Programmers Guide.