In 2005, the express tools error handler is ACET-ERROR-INIT, which I believed was changed from the original INIT_BONUS_ERROR. Are you using and old version of burst that was codes for the old bonus tool subroutines? I would expect burst to be in the new express tools or part of core autocad. Check the help files and if it is, find your old version of burst and move it or rename it so autocad won't find it first.
Dan