How to block (or unblock) the ASP.NET error logger Elmah?

Some one configured my server in a way that intentionally or inadvertently blocks ELMAH. I wish I know what that was. My current server admin can't figure out what's blocking it either.

Clues have so far

• Error message is "This type of page is not served...it has been explicitly forbidden"

• Ordinary .ashx handlers work just fine. (HelloWorld.ashx works)

• I'm running in Full Trust.

• I'm on Win 2000, IIS 5

• Machine config doesn't have any references to ELMAH (neither does my web.config)

• The ELMAH_Error table exists, but has no entries.

• My application with ELMAH works fine on my machine (i.e. shows the error log).

• I updated the Handler section to change the name to Elmha.ashx, instead of elmah.axd.

From stackoverflow

• This was happening on server I didn't have access to the windows application error log. After getting that, it was obvious that elmah and blowery were not playing well together (headers already sent errors).