In the Multiplayer server list, I've noticed if you have two of the same server addresses one of them will show a "Communication error."
This still occurs if they are different hostnames pointing to the same ip address.
EDIT: In Minecraft 1.5.1 I notice there is a slight chance that it may not happen. But still occurs often.
Environment
Windows 7
Clean Minecraft 1.4.7
Bukkit Server
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.