Ah, it's possible that ChaosGroup has only made VRay GPU compatible with texmaps they've specifically white-listed by ClassID. I wasn't aware of that until seeing the error you posted, but I now remember that they did a similar thing with certain types of scene objects (only white-listed object types are supported...for a while things like proxies and other types were not supported).
Might be worth raising the issue with them. In the meantime you'll have to stick to CPU mode to render tyBitmaps. Not much I can really do on my side since the issue is with VRay code.
One potential workaround: default Bitmaps do texture syncing with MatIDs instead of UVWs....you could experiment with changing particle MatIDs to match the frame of the sequence you want to play back, and see if the Bitmap texmap will sync to it that way....
Might be worth raising the issue with them. In the meantime you'll have to stick to CPU mode to render tyBitmaps. Not much I can really do on my side since the issue is with VRay code.
One potential workaround: default Bitmaps do texture syncing with MatIDs instead of UVWs....you could experiment with changing particle MatIDs to match the frame of the sequence you want to play back, and see if the Bitmap texmap will sync to it that way....