Addictive Drums 2 - problem with distortion

Hi there, I have a problem with distortion occurring on addictive drums, particularly on the kick drum, and it goes nuts when i play a lot of nuts fast, like it's having trouble retrieving the sample.  I am using ddrum triggers into a ddrum midi module through RME 802 with sonar x3.  When i removed the virus protection it got a lot better, but didn't stop completely, particularly on fast rolls.  I have tried changing buffers in sonar, changed the samples onto an external drive with usb3, same problem.  
My system is an i7 laptop with 16 gb ram, only about 20% of mem is in use, and with the external drive as the recording target load is practically zero.  I even tried putting the samples onto a second external hard drive, same problem! Please help!