SP2 brought with it a rather annoying tweak to the TCP/IP stack: a 10-connection-per-second limit.
I can’t remember exactly what alerted me to this problem, it may have been when a link-checker application stalled, or could have been the multi-threaded ftp client I was using.
Either way, the effect of “hitting the wall” was damned annoying and I need to find a way around it. Thankfully I found an article that offered a few solutions.