I had similar problem.
And this is my solution. I opened every table and view containing that Unknown (in your case ENROLLID) and close it immediately without making a any changes. It looks little stupid, but after that it has stop showing that error.

>I received the title error message when rebuilding my project with recompile all files. After Ignoring the error window, Project.ERR says only:
>
>Visual Class Library g:\schoolmagic\libs\abizness.vcx has the following errors:
> Unknown ENROLLID - Undefined
>
>The name in question is spelled correctly, the classlib holds all the application business objects. ENROLLID is the primary key for the most important object, and used as a view parameter in more than half the other business objects. In short, it's *everywhere* in that classlib.
>
>How do I find out where it thinks the error is, so I can fix it?
>
>Chris.