Asterisk 1.8.7.1 not registering with voip.ms

I am testing 1.8.7.1-1digium2~lucid and have not been able to register to voip.ms. My asterisk box is not behind a firewall and has direct internet access. I have confirmed that sip/udp is available on all ports:

root@home:/etc/asterisk# netstat -a | grep sip
udp        0      0 *:sip                   *:*  

My registration credentials are correct because I am able to make outgoing calls. The register appears to never go out, which prevents incoming calls. Has something changed in 1.8 from 1.6? Here is my sip.conf config

[general]
context=users
register => <REMOVED>:<REMOVED>@seattle.voip.ms:5060

[voipms]
canreinvite=no
context=users
host=seattle.voip.ms
secret=<REMOVED>  
type=peer
defaultuser=<REMOVED>   
disallow=all
allow=ulaw
fromuser=<REMOVED>  
trustrpid=yes
sendrpid=yes
insecure=invite
nat=no

If I do a tcpdump, I never see Asterisk attempt to register to voip.ms

root@home:/etc/asterisk# tcpdump -n -s 0 -A -i eth1 port 5060 
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes

Any assistance would be much appreciated, thanks!

this is not an answer to your question, but i want to know one issue , may be you can help me out. iam able to register to voip services, but my issue is that, this registration fails at times no matter what i do . i have to manually turn it up. iam using the asterisk 1.4.21.2… any idea???