was it not on the Canon Solutions disc that came with the camera? Adobe Camera Raw has no support yet for the 50D even in the new version 5 which sucks big time. I guess for now you will have to convert using the Canon software first. the same is true of most other RAW converters such as Aperture for the moment.
Edit: The only downloads I can see on the Canon site for the camera is the DPP software which should be in the camera box anyways.
Ok - so spookily - Adobe released an update to Camera Raw 4 yesterday that does support the new Canon but on their website it says the next version of ACR (5) doesnt support it.
Adobe have apparently realised the balls up and have very swiftly released ACR v5.1 to include all the new camera models that landed in the latest v.4 update. Silly billys.