I solved this problem by using an external USB self_powered Hub (belkin) at 15 Euros and by changing the buffer disk file location in the advanced preferences of Reason.
The file location was in C/ when Reason was in D/. I put in in D/ as Reason and everything works fine. It is strange that my problem was solved doing BOTH things above. It would not change anything with just one of these actions. Who cares now, IT WORKS !!