dataFilter.addRules() attributeNames hangs Firefox

hi, i followed the example from line 130:
http://docs.cksource.com/ckeditor_api/s ... in.js.html

using the data processor to rewrite attribute names..
attributeNames :
[
[ 'error', 'idt:error' ],
[ 'expression', 'idt:expression' ]
]

How do i avoid ckeditor crashing Firefox?