In EDK 6.1, although a full license has been installed for the OPB IIC v1.01.b, the timeout circuitry is enabled and the core times out after a few hours.
The OPB IIC v1.01.b pay-for-core licenses did not work properly in 6.1. In the MPD for the particular pay-for-core, add the following line:
OPTION PAY_CORE = TRUE
This problem was fixed in 6.2.