Of course, the rules of grievance of the WTO cover many fields of trade, and intellectual property is just one component of them. There have been over 400 disputes altogether, but there have been less than 30 concerning TRIPS or intellectual property as such. Canada in the past has been involved in two of those disputes, but this has been spaced over 15 years, so it's a comparatively rare occurrence. We've only had one such dispute in the last five years, for example.
On October 26th, 2010. See this statement in context.