Distortion on audio channels?

[robbocop]

This is really starting to P me off,i have Cubase vst32ver 5, 256mb ddr ram,Yamaha SW1000XG sound card,XP1600 processor.Its audio im having problems with,midi is fine.On the song im working on just now there are 3 stereo audio tracks,one bass guitar(channel 3+4) and two lead guitar tracks.(channel 7+8,9+10 respectively)If i solo any of these audio tracks the sound is perfect,no clipping/distortion at all,if i play two of the stereo tracks together distortion?Wtf!All my levels are fine,nothings clipping,i have nothing running in the background,ive twiddled with buffers etc till im sick twiddling,anyone have any suggestions?This is driving me up the wall.Any help very much appreciated!

[marnrob]

Have you looked at the levels on the output of your soundcard?

[69ShadesofRed]

Check VST Performance bar, and see if your Hard Disk is running into the red. I've noticed that on my computer anything past 50% utilization is asking for trouble. Also, 256MB of ram really is a bare minimum. You should go to at least 512MB. If the HD is being hit a lot, you can increase the memory allocation per track by going to Options->Audio->System... I don't remember what it's called but its on the upper left hand corner of the Audio settings dialog, in the same area where you set the max number of tracks.

Hope this helps.