Indeed, this is related to the bootloader as generated by mkamsboot. You'll need to either find someone else's compile of mkamsboot or compile it yourself from SVN, as advised on the wiki.
If you don't feel comfortable doing either of those, you can hold Left (|<<) or Home on the Clip+ while plugging in your DAP and this will force the original firmware to boot; you'll have to do this manually each time you wish to connect via USB until you get a chance to update your bootloader.