What will probably happen is that first your current vehicle registrations will be suspended because of the lien. Then they will suspend your drivers license because of the lien and you won't know it because the letter will be still in the mail (it's called reciprocity, heard it too many times before) Then you'll either go do 1 of 2 things:
1. You'll go to renew your reg or license and they will refuse to let you because of the lien.
2. You'll get pulled over for a minor traffic infraction and you'll find out the hard way that you have been suspended because you'll be going to jail (central booking and all if you're in NYC, bail if not in NYC).
Option 2 sux option 1 is the reverse of option 2.
So I would pay them.