machine with null serial number?

FROM : Kenny Leung
DATE : Fri Mar 28 23:15:53 2008

Hi All.

I am working on a software licensing system that keys itself to the 
serial # of a particular machine. This has been working fine, except 
we bumped into a machine with no serial #. It even shows as a blank 
on Apple System Profiler. Has anybody bumped into this, or know the 
reason why a machine might have no serial #?

Thanks!

-Kenny