ASPNETSecurity

Question

I have something odd happening in my WebApp - when I change a user's IsApproved status to 0 in the ASPNETSecurity.dbo.aspnet_Membership table, sometimes the user disappears from the table all together.  This doesn't happen every time, just once in a while.

Has anyone ever seen this happen or know what the cause could be?
Thanks and I hope I'm in the right forum for this question.  Thanks.