I would avoid making too many claims. It depends on how the insurance company categorizes the claim. I am not connected with the insurance industry in any way; however, a recent story in The Star
http://www.thestar.com/business/article/1281911 details that damage made to your car in a parking lot, when you do not have information on the other vehicle, is considered to be 50% your fault. So if they deem this to be a single vehicle at-fault claim, and you have already made two other claims in the past five years, you could be refused insurance.
I am not sure if a comprehensive claim for damage made by something other than another vehicle would be considered an at-fault claim. In order to be completely sure how this claim would be handled you should read your policy and talk with your agent before making a claim.