Virus ti problems in multi mode - no usb

[gnome]

Hi , i recently bought a secondhand virus ti and have the latest os running ( beta ) after trying the 3.003 ( latest non beta ) In both os i get digital artifacts in audio when i run 4 or more parts in multi mode.I have tested my ti alongside a freinds and his does not do this running the same os and parts and sounds ? access say its os issues ?i have a feeling there are bad virus ti's in circulation ?

i have no usb connected and use the headphones as audio out and 1 midi cable in.??is this really a multi mode synth ?