I am in the same boat.....trying to export private keys for use in blockchain.info wallet which says it will import the json dump file from pywallet.

The pywallet.py --dumpwallet was running and showing all of the data on screen. I could not find any exported .json file in either of the two Bitcoin locations on Windows. Also tried --datadir as well and didn't make a difference.
I'm not sure if this is why I'm having trouble but I did pywallet.py --dumpwallet >C:\myexp.json and it would generate everything in the format that is in the previous post with the output in a file.

When copying this text and pasting into the blockchain.info import screen it says it could not decode data. I am running the 0.6.2 client with the legacy wallet format.

Is it looking for a different format?