ok, i've found exactly where the problem is occuring. i'm going to try and get permission to post the main VI asap, but until then, i can describe the chain of VIs that results in the error:
within a while loop (with a bunch of other stuff):
shift register v -> trigger config -> DIO write -> DIO start -> DIO wait -> buffer control -> shift register ^
(where 'v' and '^' are my attempts to draw up and down arrows with text)
the first time through the loop there is also a DIO clear and DIO config before the trigger config. the error is generated inside the buffer control VI at the end of the chain.
here's the basic input information for the VIs, not counting basics like taskID
DIO config: port list={0; 0:3}, direction=output, #scans=100000
trigger config: trigger type=start trigger, mode=on
DIO write: write location={0; from start of buffer}, digital data in (program specific, i suppose)
DIO start: #scans=100000, handshake source=internal, clk freq=100000.00
DIO wait: direction=output
buffer control: control code=reserved
i know this is about the *least* convenient way for me to present this information, however, my labview programming skills are nil. i'm attempting to recreate this in an independent VI, but let's assume that i won't be successful in any reasonable amount of time 🙂
thanks again for all your help!