There normally should not be any problem using the CRM Developer Toolkit with VS2012 and TFS. I have a couple machines with this configuration.
You could try uninstalling and re-installing the Developer Toolkit.
Do you have any other add-ins that you are using with VS2012? It is conceivable that is some sort of conflict someplace. Another thing to try would be to uninstall any other add-ins and see if it works and then start installing those other items and testing
to see if one causes an issue.
Jason Lattimer
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