Which OH version are you using?
This problem looks like a known issue, that has already been solved. This problem happens if you have a quite large number of devices. If you execute a discovery the binding asks the CCU for the list of devices. The CCU returns the list together with lots of information and this can cause the problem.
If you are already using a current OH version, please set the log level to TRACE, repeat the discovery, and attach the openhab.log file.