In Winamp go to Options/Preferences/Plugins/Output and click on Configure button. Under Device tab uncheck "Allow hardware acceleration". For me that seemed to have solved this ongoing problem with UX2 (4.2.5.4 drivers) that Line 6 refused to acknowledge for a very long time. I haven't had a single sound drop out since I did that.
Also, most of the time you don't have to do a full reboot to get UX2 working again in non-ASIO applications. Just disable and reenable it in Device Manager.