I have same problem.
I485s of my family got approved on Nov 6th,2007 and the approval notice have been received.No welcome mail and no card after that.
I filed the I-90 form on Feb,2008, pending now. It is said 6-10 months needed.
I-551 stamps, temporary green card so-called, have been received at local office. My son got SSN using this evidence.
Good luck!