URW. Make sure all your URL parameters are configured properly in Google Webmaster Tool.
By default, these are set to 'Let Google Choose', but this may be dangerous if some of your parameters are sessionID or anything that has no impact on the content of the page.
Although canonical was about dealing with excess search parameters in your case, Google may have found about these extra parameters in remote ways. If so, Google will tell you it knows about them in the proper GWT page. Double-check the configuration of these parameters. Such configuration exists in Bing Webmaster too.
Better safe than sorry with Google... lol