I don't think it's 1.8.6 that breaks the google voice. Those two work fine together. I think some other dependancies must have broke between them. Are you using the Google Voice module in FreePBX by chance?
I had to compile,build & install Asterisk 1.8.6.0. I am unable to select gtalk and jabber in "make menuselect" its crossed out, to complie with it I need to install asterisk-devel but it won't let me do this as Elastix 2.2.0 RC2 has Asterisk 1.8.5.0-3 compiled with asterisk-devel 1.8.5.0.
Hope someone has gone down this path or the final release of elastix would have asterisk 1.8.6.0