Hi Brian,
If you want to try something else so you don't have to use the hub, I think I have an alternate explanation of what the root cause of the issue might be:
On Windows Vista and 7, Microsoft's USB stack appears to mishandle split-transactions. Split transactions only occur when using an EHCI (high speed) host controller with a high-speed hub and a full/low-speed device (the USB 6008 and USB 6009 are full-speed devices). The problem seems to be a race condition as it is not readily reproducible on all systems.
I believe that we have found a work around to this issue. If we only use 1 IRP for data transfer (instead of the default of using multiple IRPs) then we do not see this issue, which likely arises from support code in Windows Vista and 7 which improperly handles multiple queued IRPs.
Starting in DAQmx 9.4, you can limit the number of outstanding USB Transfer Requests. It has the downside of potentially limiting data transfer throughput. For this reason, we did not make this change a default. However, even with a single IRP, a USB-6009 should be able to sustain its max rate of just under 50 kS/s (100 kB/s).
Here is another thread where the matter is discussed, including an explanation of how to configure using a single IRP in software.
Best Regards,
John Passiak
