I've been working on the Progress Bar for a number of years, motivated by the feedback provided by the community. Before Moodle 2.0 there was little choice of how to gather data about activities in a course without snooping in database tables. This approach, however, is prone to problems, including compatibility concerns and efficiency issues.
I have therefore started a new version of the Progress Bar that relies entirely on completion called Completion Progress. This block will have the same look and feel as the Progress Bar, but will not longer have compatibility problems and will be vastly more efficient. It will also be much easier to configure, working "out-of-the-box" by relying on the settings for activity completion. Unfortunately, the new version is not backwards-compatible with the Progress Bar, so I've created it as a new plugin.
I welcome testing of this new plugin. You can download an early version of the plugin from the following link. The plugin should work with Moodle 2.7 and beyond.
I hope people find useful and simple to use. I look forward to your feedback.