In ui/joinserver.menu (in data.pk3 in the distribution), the column is wrong. It tries to sort on column 4, but pings are column 3. Perhaps there used to be an extra column which was subsequently removed. In any case, fix as so:
--- joinserver.menu.old 2006-07-18 19:17:03.000000000 -0400
+++ joinserver.menu 2006-07-18 19:17:04.000000000 -0400
@@ -411,7 +411,7 @@
action
{
play "sound/misc/menu1.wav";
- uiScript ServerSort 4;
+ uiScript ServerSort 3;
setitemcolor grpColumn backcolor 0 0 0 0;
setitemcolor pingColumn backcolor 0.3 1 1 0.5