ColdFusion Server (4.5 and 5): Using CFERROR Type='monitor' Within CFML Templates Can Cause an Error or a ColdFusion Server Crash
With ColdFusion versions 4.5 and 5, CFML templates that use CFERROR type="monitor" can cause ColdFusion server to crash (on Solaris) or throw an unexpected exception error (on Windows) if the originating error is caused by an undefined variable that was passed in a custom tag or in certain ColdFusion tags. Macromedia recommends that customers do not use CFERROR type="monitor" within CFML templates.
The article below will give more information on this bug.
ColdFusion Server (4.5 and 5): Using CFERROR Type="monitor" Within CFML Templates Can Cause an Error or a ColdFusion Server Crash