BitComet Support Team's BLOG

Windows XP SP2 limits TCP connection attempts to 10 (quite small ). If there are more concurrent TCP connection attempts, Windows generate a warnning: EventID 4226: TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts. Since XP SP2 there are only 10 concurrent TCP connection attempts possible, while in SP1 it has not been limited. (A connection attemp is a query to a computer, if it accept the TCP connection or not. If the computer is for example no more existent, it will be waited for a few seconds, until a timeout occurs and the connection attemp get canceled. )

BitComet 0.55 or above was modified for SP2 so that they can work in SP2 without any configuration. However, it may cause slow speed at the beginning of downloading, since less peers can be connected at the same time. For those behind NAT or firewalled user, a patch in the option dialog in version 0.71 or later is recommended to fix that issue.

After you applied that patch, you may need to changed the Max Simultaneous TCP connection attempts in the BitComet Options - Advanced - TCP/IP Limit.