hello all
i am the other person that kamelion mentioned, who complained about this.
i run 2 instances of mirc; 6.1 and 5.41.
after i talked with him in undernet #mirc, i found out that my connection had problems. i was connected, but it was kinda slow. from my isp's support told me that they had problem with their international links.

but this error usually comes up upon netsplits too and mostly when one of the servers that split, is the one i'm connected to.
it's strange to see one instance of mirc to disconnect (6+), while the other (5.41) one is still connected properly, with ping replies of 1 second.
as kamelion mentioned already, i have w2k pro.