Windows 8 lockout screen cutting into MP (1 Viewer)

[bopfrog]

Hi, I have been using MP 1.5 with windows 8 generally with no problems. However in the last week the W8 lockout screen has started to come up in the middle of watching things. I can get it to go back to MP (wake up?) no problem by hitting a remote button, but it is a pain in the neck. Audio just carries on and the return to viewing occurs without glitches. Seems like windows doesn't recognise that MP is running????? Maybe. Thanks for any help.