[PHP] strange error

[Leon Mergen, BlazeNetwork]

  Warning: REG_EPAREN in /home/coolguest/html/db/functions.php3 on line 13
   

What does this mean? The statement that is located there, is:

 $string = eregi_replace(">:(","<img src=\"/images/smileys/sm2.gif\" border=\"0\" 
width=\"15\" height=\"15\"",$string);

What is wrong with this? What can I do to fix it?

Thanks in advance,

Leon Mergen