Uh, what are you trying to calculate? While calculations are running it's supposed to fully utilize your CPU. If you are running complex setups then you may be running against the default memory limit of 1GB. This can cause hangs but can be easily fixed by simplifying the setup or increasing the memory limit.
If this happens while no calculations are running then please give the beta version a try, let me know if anything changes:
https://www.holdemresources.net/blog...c-public-beta/
(Some users were experiencing issues with HRC if it was open while the machine was in hibernation mode for extended periods, this might be the issue here. This is fixed in the beta version.)