First I'd like to compliment you on your effort and expertise.
Interestingly, when using the Event Reg Calendar sidebar widget I noticed after a few test clicks on scheduled events the widget would launch whatever page or post was viewed just prior to clicking the event. Example: Add Event Reg Calendar widget to sidebar.Go to Home page. Click scheduled event. Events Calendar page appears with clicked on event listed at bottom of page. Click to a post. Click sidebar widget scheduled date again and just clicked post loads. Same with a page. Hovering over or clicking the event displays http://localhost/2010/06/29/whatever-the-post-name-might-be/?month=9&d=17&year=2010&v=1. Sometimes removing the widget, reloading the page, replacing the widget clears up the issue.
I've checked networking/dns components without results in hopes of finding redirects, etc. but no luck. Also checked er_widget.inc.php and changed register_sidebar_widget("Events Registraion", "events_view_widget"); to register_sidebar_widget("Events Registration", "events_view_widget"); thinking maybe the "t" missing from Registration had something to do with it. (Don't know what I'm doing...reaching for stars...). Overall the plugin is great and I'm sure it will meet my needs.