any suggestion on my EAD problem

I sent required documents to Vermont service center to renew my EAD on May 11, 2006 by first class mail. So far, there is no receipt, no return, and check has not been cashed. I really don't know what happened. I can not check whether my package reached there because I used first class mail. It's a lesson for me, I will never use first class mail for such thing. Can I submit another application package in case that my first packge is lost or something? Thanks!