Yesterday I ran into a slight road block with simplejson. But with some playing around in the python interpreter I was able to see what the problem was with how simplejson 1.7 calls object_hook.
Take for instance the following string:
‘{”foobar”:”baz”,”comp”:{”key”:10},”array”:[10,20,30]}’
simplejson 1.3 would pass the above string into the object_hook as is. With 1.7 {u’key’: 10} is passed in first, followed by {u’foobar’: u’baz’, u’array’: [10, 20, 30], u’comp’: None}
Unfortunately, when {u’key’: 10} is passed in we have no context as to what this is.
I know, you all want to know what my solution was to the problem. 
Well, it was quite simple, I continue to look for the key “Categories”, but if the argument does not contain it, I return the string unaltered. That’s it. Now zmugfs works on Fedora Core 6 and Fedora 7.
