I've only just now become aware of this issue when I tried to use one of my GV numbers that I've not used in a while, that was then no longer working; I thought I had only to log into restart the pbxes service, which usually fixes these sorts of problems, but this time that didn't help. For me, the old GTalk connection no longer works at all, even if I try re-saving it as other replies suggest.
The switchover to the new Google SIP connection didn't work until if I changed my server to www1 (which it should be, New York/New York, closest to me), and seems to work *only* if I'm on that server; if I stay on www4, where I had been, it doesn't work at all, also tried www2 and that doesn't work either (but switch back to www1 makes it work again), and after getting to to work on www1, switching back to www4 broke it again, until I returned to www1.
The first call made from www1 generates an intrusion alert from Google that someone tried to sign into google using my password, but if I verify yes that was me, things seem OK after that (all I've been able to check so far however is that I can dial out and the receiving phone (a 3rd number of my own) will ring, I don't know either way about other problems like one party not being able to hear etc).
The above has been true for 2 different GV numbers, and 2 different pbxes accounts (each GV number attached to its own separate pbxes account, one is used for business, one for personal).