When I hard pan to the right tracks cut in and out

Have you ever had success with this? Is this a sudden problem? And what about those preference settings?

Go to control panel, then "sounds", and find the place to select windows sounds, pick no sounds. By the way, what Version of Windows are you on?

And you have no plugins on the master buss?

I am almost afraid to ask this, because this has happened to so many people (including myself...), but look at the master buss. There is a button that says mono. Is that by any chance pressed?

This is very strange. I can't even recreate this problem when I try to. Do you know what pan mode you are using? Do you see width controls in your mixer view or TCP?

This SHOULD be an easy fix, but...... something odd is happening. My next step at this point would be to open a blank project and import the audio into the new project and see if this happens again. Sometimes I have had rare issues that never were explained and went away when starting a new project. This is not hardware after all, and these zero's and ones can screw up. Rare, but I have had issues "go away" and never return. If this isn't TOO huge of a project, try importing the audio to a new project. If you don't want to try that, all I can say is wait for someone who has had the same problem chime in, this can't be a first for god's sake. As I said, this should have been an easy fix: I have seen the problem before and it has always been due to one of the things we tried. Unless it is indeed an issue with your actual hardware somehow.

Good luck. Post back if you find anything (or if you don't). I am curious now.....

There is (as mentioned) this kind of effect if mono-ing the master - panning becomes a volume control kind of. Fully panned no audio. What happends if individual tracks are mono-ed and panned fully? Would't the same thing happend on individual track as well? So look at the mono/stereo button on each tracks I/O. When importing tracks I remember some kind of option about to import as stereo or mono - or similar. Last time I remember a mono-issue the guy had routed both his lefts from soundcard to channel 1 and channel 2 - getting mono that way - getting this effect. :)

I downloaded Reaper on a different computer, started a new project, & imported my same tracks & it's working fine. Looks like it's a hardware issue with my laptop (which sucks).