I updated to Railclone 6 three days ago and noticed something wrong with the VRay GPU Interactive Mode. The IPR will render everything fine the first pass, but any subsequent modifications to the railclone object (material, geometry, move, etc...), which would normally trigger a rendering update, will get the IPR into an "infinite loop" of rendering for a second then restarting the rendering, which in turns doesn't produce any good result (you end up watching a pixelated version of your scene over and over).
I didn't have this problem with any previous version of Railclone. While I realize VRay IPR is not natively supported by 3DS Max I do feel this was a step back in productivity. I find the IPR most helpful to visualize the textures I'm creating in an efficient way. I'm hoping someone has found a turnaround for this.
Attached is an image showing how far the IPR goes before restarting.