X-Lite support forum has reported a similar problem for others and here are some suggestions:
1. Turn off QoS in Options>Advanced Menu>Quality of Service likely due to an latency on one of the hops.
2. Also other suggestions - check firewall, router and anti virus checker.
3. If none of the above work then please contact your support desk and provide us with the following information:
- Who your ISP provider is?
- What router are your using (make model)?
- Your IP address so we can investigate further.