XLite outgoing calls via 2Talk get error 408 with Zone Alarm

A week or two back I signed up at New Zealand's 2talk on the free plan to try out some funky VOIP services ... you get a free New Zealand "mobile" phone and fax number and a range of services, voice mail, call forwarding, fax mailbox etc, I'm planning to use it next time I'm on holiday/business to avoid exorbitant roaming charges. Tried out the call forwarding to my mobile, worked fine.

Just tried to call out from my laptop with X-Lite and the call didn't initiate, just got error "request timeout" and a pretty female voice saying "the other party is busy" or something like that.
I switched on the XLite diagnostic log and saw:

[07-07-22]21:07:03.059 | Info | RESIP:DUM | "Got: SipResp: 408 tid=blahblah cseq=INVITE / 1 from(wire)" | 
[07-07-22]21:07:03.060 | Info | RESIP:DUM | "Failure:  error response: SipResp: 408 tid=blahblah cseq=INVITE / 1 from(wire)" |  

Quick surf identified Zone Alarm as the culprit blocking port 5060. I couldn't work out quickly how to setup my Zone Alarm (free version) to open port 5060, so here's an alternative.
Instead of opening port 5060, you can add the 2talk server to your trusted zone.
If you make a "failed" call then open up the ZoneAlarm Control Center, click Alerts and Logs, you'll see a Blocked (under Action Taken) Incoming (under Direction) with a source IP something like 202.180.xxx.yyy :5060. Right click on that line and choose Add to Zone: Trusted.
Note that making this change allows whatever your trusted zone settings are to/from the 2talk server. And 2talk may have more servers or change them, so you may need to do this again.

Voila... outgoing calls should now work.