That looks like a server error, probably due to a certain mode set on the channel. Is the person using mIRC? Does that network allow the connection of mIRC clients via IRC, or does it prefer for you to connect through a Java client, possibly on their website?
Check out the network's website and see if you can get help there. Look for an email or form that will help. You might also go to the network's #Help channel and ask there, or some sort of oper help channel. If you don't know the network's website address, search on
Google.
G'luck!
Regards,