Guests see thumbnails but can't download attachments

[-=Sniper=-]

try using this in the same template

<if condition="$bbuserinfo['usergroupid'] == '1'"><else /><a href="attachment.php?$session[sessionurl]attachmentid=$attachment[attachmentid]"></if><img class="thumbnail" src="attachment.php?$session[sessionurl]attachmentid=$attachment[attachmentid]&amp;stc=1&amp;thumb=1" border="0" alt="<phrase 1="$attachment[filename]" 2="$attachment[counter]" 3="$attachment[filesize]">$vbphrase[image_larger_version_x_y_z]</phrase>" /><if condition="$bbuserinfo['usergroupid'] == '1'"><else /></a></if>
&nbsp;<if condition="$show['br']"><br /><br /></if>