I don't have traditional DAQ installed but in LabVIEW 7.1 and above, I was able to save without an error. I would try copying your block diagram to a new, clean, vi. Sometimes that solves the problem. Post to let us know if this helped out.
Yes I tried that. Didn't work. So I've copied/paste it to a new vi a portion at a time. Seems to have worked. Took a bit of time but it's better than doing it over. I'd just like to know why it happened. Oh well, long as it works.