Alex,i would check to make sure first you have the correct drivers,for instance the drivers you installed on windows 8,where did you obtain these?
because lik i was saying before i couldnt find your drivers on line and anything i read pointed in the direction that windows 7 they made a beta and that was the last driver version released for the EMU 0202.
check this as well,look under preferences and where it says playback,exc.
is the emu checked off as your main soundcard?
check this with audio and midi,make sure both have you emu selected in preferences/properties in sonar.
there is a driver conflict happening and we can see if we can narrow it down and find the offender and get you back to enjoy music rather than rebooting.
for now instead of re-booting alex,try to just log off instead.
log off/log back on windows 8
its almost the same as rebooting minus the power down/up.
the next time this happens it also might be worth it to go into your computers properties/device manager and look at the soundcard driver,is there a yellow mark next to it?
this shows a driver issue.