I have interfaced a HID bar-code scanner with LPC2468 using interrupt transfer. The polling interval which i receive(from bar-code) in the Endpoint Descriptor is 10 ms. What will happen if i increase or decrease this polling interval.
If you poll if more/less frequently, assuming it is ready to send data, then it will simply be a case of receiving data more or less frequently.
I'm not sure if you have read this programming manual, but if you haven't then you should. It appears (at a glance) that it is configured using the barcodes themselves (as opposed to a message from the PC.
All the configuration barcodes are there, and there is a section on changing the inter-message delay. I would try using these (set delay to 0 between messages), poll at your desired speed (up to 1 / 330 = ~3ms polling interval) and let us know how it goes.
Here is a clip of some relevant settings in the "General Configuration" section (note the "start of configuration" and "end of configuration" barcodes):