controllers loosing touch

[RePeter]

this has happened to me the last two times i have played out in front of a crowd.....

playing a live set using a laptop running live and plogue, controlling with a x-session and a microkontrol (both running over usb)

at some point during my set i seem to loose the connection between the laptop and my controllers. unfortunatly this means that i need to stop my set (usually by mixing into a CD) rebooting the laptop and live again.

the power to the controllers is fine, i.e. they both have all their lights still on, just that all of a sudden they live stops recieving the midi messages. this affects both controllers, which makes me think this is a problem with my laptop or possibly live/plogue.
my best guess so far is a small power fluctuation, causing the laptop to be unable to supply power over the usb cable, and thus loosing contact altogether.

this is only a small problem, live still continues to run smoothly, and mixing out to a cd is fine with me, however im a bit worried that next time its going to happen in the middle of a mental filter sweep and im going to send the crowd deaf!

any ideas or suggestions?