Cisco 7940G with Sipgate - no audio on incoming calls

I have a Cisco 7940G phone with SIP firmware 8.6 running on it, through a Netgear WGT624 v3 Router. I have two lines, one which is registered with Sipgate, and one which is registered with GCI Com (Skype 0207 transfer).

I have been able to make calls out with the Sipgate line (line 1) without any problems. However, as soon as I get an incoming call, I can answer it, but the line has no audio, both incoming and outgoing.

On the GCI Com line I am unable to make any calls at all, both incoming and outgoing.

Here is my configuration:

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SIPDefault.cnf:
image_version: P0S3-08-6-00
proxy_register: 1
timer_register_expires: 3600
preferred_codec: g711ulaw
dtmf_inband: 1
dtmf_outofband: none
dtmf_db_level: 3
timer_t1: 500
timer_t2: 4000
sip_retx: 10
sip_invite_retx: 6
timer_invite_expires: 180
dial_template: dialplan
tftp_cfg_dir: ""
sntp_server: "194.81.227.227"
sntp_mode: unicast
time_zone: GMT
dst_offset: 1
dst_start_month: March
dst_start_day_of_week: Sun
dst_start_week_of_month: 8
dst_start_time: 01
dst_stop_month: Oct
dst_stop_day_of_week: Sun
dst_stop_week_of_month: 8
dst_stop_time: 02
dst_auto_adjust: 1
time_format_24hr: 1
date_format : D/M/Y
dnd_control: 0
callerid_blocking: 0
anonymous_call_block: 0
dtmf_avt_payload: 101
sync: 1
enable_vad: 0
nat_enable: 1
voip_control_port: 5060
start_media_port: 8000
end_media_port : 8012
nat_received_processing: 0
outbound_proxy_port: 5082
cnf_join_enable : 0
semi_attended_transfer: 0
telnet_level: 2
remote_party_id: 1
call_hold_ringback: 0

logo_url: "http://10.0.0.11/cisco/aah.bmp"
logo_url: "10-20logo.bmp"
------------------------------------

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SIP0000000000000000.cnf:
line1_name : 5980--- ; SIPgate device ID#
line1_authname : 5980--- ; SIPgate device ID# again
line1_password : -------- ; SIPgate device password
line1_shortname : "Oxford"
line1_displayname : "Oxford"
proxy1_address : "sipgate.co.uk"
proxy1_port : 5060

line2_name : 44207870---- ; SIPgate device ID#
line2_authname : 44207870---- ; SIPgate device ID# again
line2_password : --------- ; SIPgate device password
line2_shortname : "London"
line2_displayname : London"
proxy2_address : "sip.talksense.com"
proxy2_port : 5060

phone_password: "cisco"
------------------------------------

Any help would be greatly appreciated.

Tim

Downgraded from 8.6 to 8.2 and that solved it.

Tim