Gilles:

Im getting the same error. My system is 6.4.0 and my header files are correct. 
The code does a number of smaller, less than the 64 bytes, writes and works. However whan I try to do a write of 63.4K .
 It fails. with an 0x2000010.  A Complete with error and NO_MEM_FOR_TRANSFER. 

I used usbd_alloc to create the block of data to be written. 
The usbd_io call returned EOK, and the bulk output callback is called. In  the callback, usbd_urb_status gives the 
0x2000010 status and zero bytes as the length. 

What does the error mean? Where is there not enough memory? and most importantly, how can it be overcome. 

Thanks,
Andy