I keep having this one problem when entering contacts into Outlook 2003.

I am entering my customers data into outlook's OWN contact form not one that
i have created my self. When it comes to the email part of the form, I enter
the email and click or tab to the line below it so that i can continue with
entering information, outlook erases the email and will not keep it in that
contact. SO again every time i am entering an email address in the proper
format of an email, outlook deletes the email from the line that i enter it,
and will not allow me to add that email address to the contact file. WHAT'S
GOING ON can some one help me.