My friend was put on hold for an interview. It went well past the 4 -6 week time period. After 11 weeks I told her to call them and see if she could get an interview. She called, they had a cancelation and got her in the next day, she was then given an acceptance to the school. If she hadn't called she more than likely was going to be lost in the mounds of uninterviewed applicants.
However.... this was in March, so unless you are interviewing in the same area and are coming from out of town, I would not suggest calling for an interview this early in the process.
Oh, the school was MCV.