Hi Susan Well, I'm sure we'll get to the bottom of this. First of all:- I'm assuming the following:- 1. Firmware on BCR is 1.10 and not an earlier version. It shows you when you turn it on 2. Behringer MIDI driver is most recent version - hasn't been updated for quite a while, mind you. In device manager it should report as version 1.2.1.3 (on XP, at any rate) 3. You're running on a 32 bit OS either Win XP SP2 or greater or Vista, preerably at SP1. I developed and tested on Win XP SP2 and Vista SP1. It may work with a 64 bit OS but I have done no testing on this. 4. Reaper is a reasonably recent version. I'm currently on 3.1415 5. You're connecting the BCR directly via USB in mode U-1 - you've confirmed this already, I'm pretty sure, and there are no MIDI connections to the unit's MIDI ports. And you've reconfigured the BCR to another operating mode, saved that mode, cycled power to the unit then set it back to U-1 with Reaper not running and then gone back in to Reaper again, right? 6. The USB port you are using is one of the computer's primary USB ports and not on a breakout card or via a hub. Now, I am using a hub with no problems but sometimes weird things happen and changing USB ports fixes it. Worth a try. 7. You can reproduce the problem with an empty Reaper project. In that case, the left hand top encoder should control master volume with no Reaper tracks. Does this also not work?. Now, assuming all the above, it looks like Reaper is somehow 'out by one' when it reports the MIDI event to the CS software. This kind of sounds like a weird buffering issue, so that when I rotate an encoder, the events that transmit the changing MIDI values don't all get to the CS plugin. Ah.... I just had a thought. What's your 'control surface update frequency' set to on the control surface dialogue. It should be 15Hz. If it is, try changing it to a faster or slower refresh rate. Does this affect the problem Also, what do the switches do?. If you mute or solo a track, does this work properly. Is it just the encoders?. Finally. If you are running any kind of Antivirus software, try disabling it temporarily. AV software can do horribly strange things. Also what happens when you move the faders in Reaper. Does the BCR track smoothly on the encoders I've just gone back and double-checked all is well on both my machines, so I definitely cannot reproduce this - but I'm sure we'll get to the bottom of it.