I have not seen any similar reports (and I cannot try Amplitube myself), so it would be good if someone else that uses (or has tried) Amplitube with kX 3541, could respond and let us know if they have the same problem, etc.
BTW: If you are familair with
DebugView, you might try capturing any debug output from kX and Amplitube to see if it gives any clue as to what the problem is.