I've recently migrated a trac project to a new machine and now the roadmap progress bars are not displayed. I've tried enabling and disabling RoadmapModule under the Admin -> General -> Plugins -> Trac 0.12.3 menu. I've also checked the project file trac.ini contains:
[milestone]
stats_provider = DefaultTicketGroupStatsProvider
Turns out it was missing plug-in causing compatibility issues.
sudo easy_install -U -Z http://trac-hacks.org/svn/typedticketworkflowplugin/0.11