Error log filled up with a PHP warning

The following ERROR message is filling up my Error Log. It not coming all the time, but when it appears there is 26 messages in a row:

[2010-08-06 02:13:37] (ERROR @ /path/to/core/xpdo/xpdo.class.php : 1668) PHP warning: json_encode() [<a href=’function.json-encode’>function.json-encode</a>]: recursion detected

Anyone who knows what this can be related to? The manager or the front-end?

I’m getting this as well. (MAMP 1.9, very basic Revo install with ’typical’ packages installed).

Maybe this thread, to do with TinyMCE I think :_
http://modxcms.com/forums/index.php?topic=52935.0

Thanks for the link - makes sense now (unlike a whole heap of other things, but I muddle through, sort of, fx:sigh ).