The displayed private key is probably raw hex.
I haven't looked at blockchain.info's new wallet service in a couple of days, but unless they've changed it very recently it's probably raw base58:
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Blockchain.info in their infinite wisdom has abandoned the more traditional representations of bitcoin private keys (such as WIF and HEX) and instead decided to display private keys as a base58 value with no version, checksum, or compression indicators. I'm sure someone over there probably thought it would be a good idea, but I don't know why.
Therefore it seems that anyone running the latest blockchain.info web interface doesn't have access to the more traditional and multisystem-compatible formats. I'm sure there will soon be several converters written to help people with this problem.
Of course "soon" will depend on how soon someone with the technical knowledge feels motivated to do so, and also depends on whether or not blockchain.info decides to abandon this folly and provide more traditional private key representations.