I sent an email to Line 6 support a week ago to see if they could help me but they did not solve the problem at all.
They told me to copy the drivers to a USB key and install them from there, then to try on another computer but it didn't work neither... I've tried on Windows XP then on another Macbook, but with the latest OS which is different from mine (Yosemite).
I'm sure the issue doesn't come from the gear. I mean even if I don't connect the UX2 to the computer, Line 6 Monkey is unable to recognize the correct installation of the drivers.
Seriously, I am so pissed of against Line 6 right now. Paying 170€ for a plastic device that have worked like twice a year (for 3 years) is a bit exaggerated...