I have another method to fix the problem.
Just use decrypt_gpi.exe on locked or unlocked cyclops gpi file and it works on old or new firmware (no .unl file required)
I found this out by accident some time ago but there was no reason to post.
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This tool was originally posted by syzygy
Maybe if it works for all Nuvi's you could post locked unlocked and decrypted cyclops.
I think that it works on any encrypted .GPI file (untested)