Today I was working with my Nokia E61. I was able to register it to my asterisk server. I was able to receive calls. However I cannot call out. Whenever I do attempt to call out I get this error in the asterisk console:

[Apr 23 14:30:30] WARNING[2707]: app_dial.c:1745 dial_exec_full: Unable to create channel of type 'SIP' (cause 20 - Unknown)
[Apr 23 14:32:11] WARNING[2712]: app_dial.c:1745 dial_exec_full: Unable to create channel of type 'SIP' (cause 20 - Unknown)
[Apr 23 14:34:45] WARNING[2734]: app_dial.c:1745 dial_exec_full: Unable to create channel of type 'SIP' (cause 20 - Unknown)