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I installed and briefly used ZenTrack. It lacks much of the functionality that you would expect to find in a mid-level help desk solution, however, it does perform the basics. It is free after all...
The blank page you are seeing is probably due to permissions, make sure you read the installation document thoroughly; it covers everything you need to do in order to get running.
There is also a mod you should check out called Mantis Bug Tracker.