There was a change in the representation of a steamid first in TF2 and now in the Source SDK 2013.
Steamids are rendered differently by the game. Instead of STEAM_0:X:Y it's now [U:1:Z].
SourceMod 1.6.2 works around this change transparently for plugins by always providing the "old" STEAM_X representation, so there are no changes needed on the plugin side.
The webpanel was parsing the "status" command output to find right player to kick and couldn't handle the new [U:1:Z] format.
The attached .zip includes the necassary changes to support both steamid formats and fixes the kicking of players through the player context menu on the servers page as well as viewing the player's community profile.
Download the attached .zip and extract the contents in your installation of SourceBans 1.4.11. Overwrite all files.
To check the actual modifications, have a look at revisions 163 and 164 in the SVN