Signing / Verify an address to claim my clams.

I have some old paperwallets that are still in use, so I'd rather not expose any information outside of a signed message, using an offline computer running brainwallet software.

However, I open the software, change the network to CLAM, and then sign a very basic message - it is during the verification process on my QT client that I get a verification failure error.

I have even performed this in 'reverse'.  Basically signing a message on the QT client, just to be sure that the data elements that I'm using are in fact correct.  Any ideas greatly appreciated.

Running The CLAM Client v.1.4.17 (aka QT client).