Zone Propogation to Root .com Servers

[dennis]

I'm hoping someone can help with a problem I'm seeing on a customer system --

They have a .com domain set up with zone a file that appears to be working
100% properly on the surface.  They've recently outsourced hosting of their
web site.  'www' was previously assigned an 'IN A' record in the zone file
and hosted on an internal machine, similar to the following:

www    IN    A    111.222.333.444 (some internal IP address)

Upon transfer of their website, they changed the zone file as follows:

www    IN    A    555.666.777.888 (IP of new web host provider)

This appears to work for internal machines and for the host provider (who is
also a secondary DNS).  All online DNS-check tools report the proper www
server name when queried, as do direct queries from the primary/slave
servers.  The problem lies with the GTLD-SERVERS.NET-series root servers,
which continue to report 111.222.333.444 as 'www' (the old internal IP
address).

The web provider insists it is an issue of propagation, but the problem
persists after 2 months.

Zone transfers are restricted only the slave DNS server.  Could this be the
problem?  If not, can anyone offer a possible avenue of investigation?

Many thanks.