I think this is Template issue ! check your theme.php
you should have this under your theme.php
if (!isset($template_add_your_comment)) //{THEMES}
$template_add_your_comment = <<<EOT
<form method="post" name="post" action="db_input.php">
<table align="center" width="{WIDTH}" cellspacing="1" cellpadding="0" class="maintable">
<tr>
<td width="100%" class="tableh2_compact"><b>{ADD_YOUR_COMMENT}</b></td>
</tr>
<tr>
<td colspan="1">
<table width="100%" cellpadding="0" cellspacing="0">
<!-- BEGIN user_name_input -->
<tr>
<td class="tableb_compact">
{NAME}
</td>
<td class="tableb_compact">
<input type="text" class="textinput" name="msg_author" size="10" maxlength="20" value="{USER_NAME}" />
</td>
<!-- END user_name_input -->
<!-- BEGIN input_box_smilies -->
<td class="tableb_compact">
{COMMENT}
</td>
<td width="100%" class="tableb_compact">
<input type="text" class="textinput" id="message" name="msg_body" onselect="storeCaret_post(this);" onclick="storeCaret_post(this);" onkeyup="storeCaret_post(this);" maxlength="{MAX_COM_LENGTH}" style="width: 100%;" />
</td>
<!-- END input_box_smilies -->
<!-- BEGIN input_box_no_smilies -->
<td class="tableb_compact">
{COMMENT}
</td>
<td width="100%" class="tableb_compact">
<input type="text" class="textinput" id="message" name="msg_body" maxlength="{MAX_COM_LENGTH}" style="width: 100%;" />
</td>
<!-- END input_box_no_smilies -->
<td class="tableb_compact">
<input type="hidden" name="event" value="comment" />
<input type="hidden" name="pid" value="{PIC_ID}" />
<input type="submit" class="comment_button" name="submit" value="{OK}" />
</td>
</tr>
</table>
</td>
</tr>
<!-- BEGIN smilies -->
<tr>
<td width="100%" class="tableb_compact">
{SMILIES}
</td>
</tr>
<!-- END smilies -->
</table>
</form>
EOT;
also check your {Admin mode}=>config =>comment setting =>Allow smiles in comments value to be "yes"