Drum Crash

XP SP3
9.5 r1598

When I try to enter drum notes by going to the appropriate place in time and double clicking, the first instrumrnt (Closed Hi-Hat) seems to be okay. However when I try to add a 2nd Instrument on a different beat (Pedal Hi_Hat), the layer automatically changes to layer 2, allows me to add 1 note and crashes,

Thanks.