I used to get this 10053 error occoasionaly on most of the networks I frequent, but most often on one particular network anywhere between 1 to 4 disconnects every hour (just idling, unjoined).
After upgrading to version 6.3 from v.6.21 I haven't encountered it yet for over a day.. so it seems something has changed in mIRC v.6.3 to help with this issue for me at least.