Thanks a lot for the tip! It worked! the speed increased from an average of 200kb\s to 1mb\s. Great!

the "segment buffers" option was unchecked beforehand. I checked it and increased the buffer to 128 and it immediatly helped improve the speed. Now I can download my purchases with ease (and in non-raw video).

Too bad Amazon Prime titles don't work. It always outputs "can't find the decryption key"...