Strange Problem with Voxalot Registration
 

I am using Sipua 1001 wih voxalot. I am facing a very strange problem.

I am using us.voxalot.com as proxy and sometimes the ATA refuses to register at this proxy and if I chage the proxy to voxalot.com it registers.

After sometime (hours to a day or two) the same problem repeats with voxalot.com proxy and then if I change the proxy to us.voxalot.com it starts working again. Is anybody else facing the same problem, Can somebody please help me on this issue, thanks