Apparently, a setting in your CMOS Setup panel got changed, perhaps before the freezing occurred, or when you forced the shutdown. The CMOS Setup panel is where you change settings in your BIOS. Your computer's BIOS probably has various settings for CPU speed or "frequency", and it somehow got changed to a faster speed than appropriate for your specific processor. Thus, the overclocking message.
Since you selected Default settings and it's running fine now, you should be OK. However, if this happens again and becomes a recurring problem, come back to the forum for further discussion of the issue.