SVN 1.6.2 => 1.8 => 1.6.2 "not acceptable here"

Asterisk 1.6.2 from SVN works fine.
Decided to try 1.8 version, installed correctly. Stripped modules from old before new install.
I did not install new *.conf files, left old ones intact.
1.8 starts up normally.
Try to call from one local extension to another. Asterisk denies the call with “not acceptable here”.
I read that this can be due to codec not supported, but everything here uses u-law and works good in 1.6.2.
For now I am back with 1.6.2, which again is working fine. Next avenue is to look at the SIP DEBUG options in 1.8.
Have there been any major changes to the .conf files that I should be taking into account?

This seems to be related to the phone I am using to make the call.
If I call from a Nokia E71 to Asterisk 1.8 to Snom 360 it works fine.
Reverse the process and the call fails.
I read that there are some issues with Snom and Asterisk 1.8 related to SRTP.
I did download SRTP before compile and this may have made the situation worse.

Now resolved. Forced re-registration of the phone allowed it to work correctly with 1.8.