What error code are you getting? (is it code 10? Device cannot start?)
One trouble with using Interrupt or isochronous endpoint for that matter is, if the host doesn't have enough bandwidth to guarantee bandwidth for these endpoints then it'll not configure the device.
as per the Spec, The maximum allowable burst size for interrupt endpoints is three. What value are you setting it to?
I set the burst length to 3 and it is good now. Where can I find this information? Where can I download the spec?