I'm taking a look at the "Projects I'm On" filter that is default to the system -- assuming they use the same one on the widget, the filter acts in the following way:
* projects you own
* projects where you're listed as the sponsor
* projects you created
* projects where you're on the project users list
Outside of the first three bullets, the fourth one is usually the problem. I've seen some teams decide that the way to "share" a project with someone is to add them to the project's People section. Other teams occasionally accidentally leave someone in that section and further compound the error by creating a template that also contains that user. Next thing you know, the same user has been haplessly added to everything. This does tend to make the "Projects I'm On" filter quite messy.
The only way I know of to filter it out is to create your own filter, defining exactly what you want "projects I'm on" to mean, and coach your users to ignore the large, default button in the widget.
