The Revit Clinic confirmed an issue I've been seeing for some time now. I thought I wrote about it in the past but it seems that I haven't. If you click on a central file (2010 and 2011) Revit detects this and checks the Create New Local option.
If you find this option disabled (gray'd out) then that's a clue that something is wrong. The situation I've observed and the clinic's first listed problem is that Revit thinks that your computer is finding the central using a different path than other members of the team that have also created local files. In my case I usually find that someone is showing a path that reflects the Network Neighborhood path instead of a formal Drive Letter mapping. In a couple of other cases I've encountered a specific IP address instead.
A post yesterday at The Revit Clinic confirmed that these issues are indeed a problem for Revit when we intend to create a local file. If you find the Create Local File option disabled, STOP. Get some help to fix your path before you find yourself unable to Synchronize with Central.
There are two other explanations offered in The Revit Clinic's post; worksharing isn't enabled and a corrupt central file/thumbnail issue. I've also observed that the so called corrupt central file is occasionally really a local file. In this situation someone saved their local file in the folder where the central file was and chose to overwrite the file. The unfortunate consequence of this is that nobody else can synchronize with central because it isn't a central file anymore. Take care, it's dangerous out there folks.