Now the tip. When you insert the emoticon from the list, it writes in the post in lower case automatically, however as Sabrina suggested, it must be in uppeer case. So it is better to write it :RONTFLMAO: not :rotflmao:
This is how it worked for me. The glitch in the system is that if you select it from the list, it uses lower case in the code which fails to load the emoticon correctly.