Whois at Netsol - wrong IP address for nameserver?

[myOstrich Internet Domain Manager]

One of my customers has domains both here and at Netsol, and has asked 
me a question I can't answer. I'm hoping one of you has seen this and 
has an answer for me.

The domain that his nameserver is on is here.

He changed the namserver IP address about a month ago.

The correct nameserver IP address is listed in a Tucows WHOIS display 
for any domain that is also registered at OpenSRS.

For his domains registered at Netsol, the WHOIS shows the correct 
nameserver name, but the wrong nameserver IP address.

What's up with that?  Shoudn't the IP address in the WHOIS display be 
coming from the root servers and be the correct IP address for his 
nameserver? Does Netsol's WHOIS use a cache of data for nameserver IP 
addresses? What triggers them to update this?

I've sent a note to Netsol support but I have little faith in getting a 
response anytime soon since I'm not a customer.

Thanks,

-t