We've seen this a few times, where certain projects end up with a few parameters called "Extensions.Buffer, etc." As far as we've seen, there is no way to purge these parameters. Are we alone on this? Can you get rid of them? Are they a bi-product of certain Add-Ins (2009: Model Review and Revit Extensions). They don't appear under Project Parameters, and you can't delete them with something like a schedule dialog (Fields - Delete).
I've attached a window showing some of the parameters.