sounds intercept each other

[haNOK]

so im using ableton lite 9 live and whenever i am trying to make beats with two different sounds (drum set and an instrument set) the sounds cut each other off so the drum continues to sound normal but the instrument set starts to cut off and create a distorted noise. what is happening?
also i cannot seem to utilise my MIDI device consistantly as it wokrs on days and others it does not.

[Great Bear]

Sounds like you've got your audio buffering set too low in the preferences.