I recall this note from a while ago:
The Cisco Unified IP Phone 7960G
NOTE: This product is no longer being sold and might not be supported.
I recall being disappointed that there were no new firmware loads for 7960 when upgrading to CUCM 8.6. The best solution might be to get the customer to upgrade the ip phone. I recall from a bootcamp that 7940s/7960s were not recommended for a lab because they were not able to display some of the calling party transformations we were studying.
Just throwing a dart: Did you try placing the identical value in Alerting name as in ASCII Alerting Name? I routinely do that as SOP. You probably do too.