[Radiant] Problems using word "echo" in body? (no filter)

[Jon Baer]

I can't figure this out but I recently tried to add a post to  
something and kept getting this error:

Precondition Failed
The precondition on the request for the URL /admin/pages/edit/16  
evaluated to false.

Which Ive never seen before + traced it back to the fact that its  
caused using something like this in your template:

echo x

This is without using a filter.

Any ideas?  (I searched ml archives and only saw a few parsing  
bugs).  Using 0.5.2.

Thanks.

- Jon