Without knowing what your XP firewall settings are, i'm not really able to answer why it stopped you connecting to Irc servers, perhaps you had previously configured it to allow an irc service, to run.
The error that you got 10053 is explained in detail here
web page Berkeley description: A connection abort was caused internal to your host machine. The software caused a connection abort because there is no space on the socket's queue and the socket cannot receive further connections
Everyone has a different idea on this error IMHO it's a winsock fault
There is an ongoing argument as to wether there is a permanent fix for it, see this thread
web page Anyway glad you are now re-connected with mIRC happy Ircing
ScoT
#mIRC Undernet