I am using maskedtextbox controls for a phone number. I have the same code on multiple pages but on one of them, the value of the maskedtextbox controls are cleared on postback. All the other places with the same exact code (copy and pasted) are working fine but for some reason the values are cleared on one page. The bug has to do with the control being on the Login page before you login (it is used during registration). I took out the Forms Authentication, and the values were no longer cleared on the login page on postback. I am able to get around this by just taking the register page out of the part of my application that needs to be authenticated, but it is a bug that should be fixed.