Jay,
Are you by chance on Linux? I have seen what you describe on Linux, not on Windows. On Linux, the FTDI USB driver does have throughput/buffer issues for high throughput devices.
If you are on Windows, do you know which error code is being returned? The problem corrects itself on the next sweep? You could try a couple troubleshooting steps we suggest for customers who are having USB issues, such as, enabling the “High Performance” power plan in the “Power Options” control panel menu, and disabling any anti-virus you might be running.
Regards,
Andrew
