Text in the password text box disappears

Hi friends,
                 I have a problem with password textmode...When debugging  my .aspx page , the text entered in the password box disappears...In single or multiline mode, there is no problem..the text disappears when an event occurs(for eg. when a button is clicked)....So, I have to retype the text in the password box to insert the data into a databsase..Why this problem occurs?..How it can be avoided?..pls help me
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