Pretty unusual then. Do you have any other (non Red Gate) SSMS add-ins installed?
One option may be to try downloading a trial of our ANTS Performance Profiler, and profiling SSMS. This might show whereabouts in the execution excessive CPU is occurring.
If that works, you can save the results, zip them, and mail them to email@example.com
quoting F0071759 in the subject line.