/rcinstall/error_log
I cleared the log, re-enabled the plugin, entered the g_c login info (which I know to be valid), click on AB/Google Contacts and it throws the error.
Return to the log, no entry showing.
debug_level is set to "1"
Running on what I think is Redhat at Bluehost:
PHP version 5.2.17
MySQL version 5.1.65-community-log
Architecture x86_64
Operating system linux