You have to edit the CSS file to make it work...

Find this in the new CSS-file that comes with 2.11 and copy this part in your own CSS-file (or use the downloaded version)

#codepicker              { position:absolute;  background:#ffffff; border:1px solid #E45000; display:none; padding:0; }
#codepicker ul           { list-style-type:none; margin:0; padding:0; }
#codepicker ul a         { color:#000000; display:block; text-decoration:none; padding:1px 5px 1px 5px; }
#codepicker ul a:hover   { background:#FFF6EF; }

Do not mind the colors used here, these are used on my forum.

Basically you should update all files and if you use the original forum (template et all) then this is what you always should do. The changelog file is not always complete...

Bert