Dell Voice App not answering incoming calls

[blyefd]

Hi,

I have the Dell Voice app on my android phone (nexus s, android ice cream sandwich) and it does not answer incoming calls. It just rings and goes to voicemail. However sometimes about 3-5 minutes later, the Dell Voice app will ring with the previous call, but when answered obviously the call is silent.

I have forwarded many ports on my router: 13000, 13001, 5060, 5061, 6060, 6061, 16384-16482, (from another post). Does not make any difference.

It also does not make any difference if I am on wifi or 3G data.

Calling out works just fine.

Can someone help me with this problem?

thanks