thanks all! yeah, two green lights, so no connection or power issues, and fresh install and updates, so workbench, monkey, and java all current. it *was* possible to circumvent the error to get to workbench, but not to reach the guitar's patches.
BUT i just got it to work. only thing i can think of is that Automap may have changed? my Novation keyboard uses it to communicate controller data with my software.
no idea how to handle this if Novation and Line 6 data don't get along for some reason :/ (have fiddled with Automap since having the problem, but didn't think i'd changed any settings; also, i'm not trying to use the keyboard and guitar concurrently or anything like that).