When I connect the DA100 via RS-232-C and use DAQ32 Plus to acquire data, the performance bar goes to OVER and I lose data. What should I do?

Because DAQ32 Plus has greater functionality than DAQ32, it requires that much more CPU speed and memory. If there was no problem on DAQ32 but the performance bar goes to OVER on DAQ32 Plus, probably the baud rate set on DAQ32 is too slow for DAQ32 Plus. Try raising the baud rate. If that doesn't improve the situation, consider raising the PC's performance by increasing its memory and by other means.