Is there a limitation to the number of calendars that iCal can manage?

My wife and I share calendars. Recently she found that one of my calendars was not showing up on her iMac and any dates or appointments were automatically sent to Notifications. However, all of my calendars and hers as well show up on her iPhone and iPad. With that we took her iMac to a Genius Bar. The tech after trying many things determined that because the age of her iMac (a 24", dual core) was limiting iCal to 10 calendars. I find this incredible. I can't image that this could be a hardware problem. She and both are running under Mountain Lion. Has anyone ever heard of this issue?