i see what your saying, although i dont have a solution for you...

realy i'm a bit suprized that mirc alowed you to creat the dcc chat window while having an fserv window open .. unfortuantly i dont have the ability to do any testing right now to try to find a work around ..

i know there is a queryrn command but i doubt it works for dcc chats .. if it did though u could rename the dcc chat window ..

unless someone else knows somethign i dont u might wana put this in the bug reports section.