Using CER 7.1.1.10000-5 with CallManager 7.1.2.31900-1, I've tried using the AdminUtility to change CER to CallManager version 7.1 and 7.0 with no luck as I read another post that suggested trying that. I have CER 7.1.1-10000-5 in the lab with CallManager 7.1.3-10000-11 with no JTAPI problems...
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2010-02-08 15:52:18,236 | WARN | CER_TELEPHONY | Failed to get the JTAPI Provider for : 10.20.188.13 trying infinitely
2010-02-08 15:53:10,115 | WARN | CER_AGGREGATOR | CERServer could not communicate with CERPhoneTrackingEngine.