The NI 9219 has a max rate of 100Hz in High Speed mode. If you're running your AI task faster than that and have no other modules in the task, you are wasting bandwidth returning repeated samples.
It is possible to max out your USB bandwidth with a single digital module in a cDAQ-9172 chassis but even doing that your computer should still be responsive. The most likely culprit is wasteful code. Without seeing your code I can't say for sure but common mistakes include having a read in a loop with no delay, constanty stopping and restarting tasks (state transitions should be outside of loops), and excessive in line data analysis.
