I think I found a bug in "smilies.inc.php". Here is the code
line 163:
Quoteif (document.$form.$field.createTextRange && document.post.message.caretPos) {
it must be
Quoteif (document.$form.$field.createTextRange && document.$form.$field.caretPos) {
it work fine with comment, but not with my forum plugin.
Applied suggested fix to code in SVN repository both for cpg1.4.x as well as cpg1.5.x, so this will go into cpg1.4.20 and cpg1.5.0 and better.