Finally got it resolved. Thanks to Don at Line 6 support for some helpful pointers including the command line uninstall. Didn't solve my problem, but pointed me in a direction. What I did was uninstall the driver portions of the install. No dice. I also removed the Avid Core audio driver. No dice. Also manually removed an old hardware interface driver that was still there from changing out another audio I/O interface recently. No dice. Rebooted. No dice. Panic. Went into safe mode. Managed to run the Line 6 uninstaller. No dice. Took a long hard stare at the kernel panic at boot (which I'd taken a picture of). Wondered if I was being misled. Seemed to be that just after the Line 6 driver loaded, and the UX 8 went from flashing to recognized, was the panic. However. I figured that maybe that was a red herring. What I was seeing was a video driver panicing. Just thought it was coincidental, but, it wasn't... (at least it appears). The Avatron Air Display driver was the culprit. It *sometimes* allowed a boot (or did once), but removed it using the uninstall script in safe mode, and ... BINGO! I am now up in Yosemite (without having to do a complete fresh from scratch install of Yosemite, which was also Don's only other recommendation - and for understandable reasons - he wasn't just reading a support script. Doing that would have cost me many days of reinstalling software, multiple DAWs, (7) plugins, interface drivers, Siblius, Finale, Notion, etc. etc. Not a real option for me and keep running meantime). So, there you have it. For those who need the command line things to completely clean Line 6 stuff, here they are: "Here are the folder locations that POD Farm 2 will install into. Please search the following file locations on your MAC and remove ALL Line 6 software, and ONLY Line 6 software from these locations, be careful not to remove things that are related to other programs: •Library/Audio/Plugin-Ins/Components •Library/Audio/Plugin-Ins/VST •Library/Audio/MIDI Drivers •Library/Frameworks (look for L6WXTG and L6WXTY.framework and delete them) •Library/Application Support/Line 6 •Library/Application Support/Digidesign/Plug-Ins •User/Library/Application Support/Line 6 •Applications/Line 6 •User/Documents/Line 6 •User/Library/Preferences (Line6 preferences, should be something like com.line6.xxxxx, etc. Delete.) Open the disc utility program located within your utilities folder, select your primary hard drive, and repair disc permissions. Restart the computer."
Kind regards
Derek.