I'll try to clear up some of the issue raised in this thread.
Camera Raw 6.1 & Lightroom 3.0 shipped lens profiles for all five Canon 70-200 lenses. They are available when you are processing raw files.
CR & LR try to find the correct lens profile automatically, based on the available metadata from the image that you are processing. Around 2005 (e.g., Canon EOS 5D), Canon began embedding strings in their raw files to identify the lens used to shoot the image. So for Canon EOS models since ~2005 shot with Canon lenses, CR/LR will find the profile automatically (assuming we have a profile for the lens in question).
The 1D Mark III is an example of a camera that shipped after 2005, has the required metadata, and hence CR/LR is finding the profile automatically.
The 20D is an example of an older model (shipped prior to 2005), without the definitive metadata, and hence CR/LR is not picking the profile automatically. Basically, CR/LR only "knows" that you shot the image with a "70-200" lens, but there are many 70-200 lenses out there (some made by Canon, some made by third parties) and CR/LR cannot be sure which specific one you used. So, rather than guess and possibly (likely) get it wrong, CR/LR is conservative and refuses to pick the profile in these ambiguous cases. What you can do in these cases is pick the profile manually. You can also choose "Save New Lens Profile Defaults" from the Setup menu to ask CR/LR to "remember" your profile choice, so you don't have to keep picking the profile manually in the future.
Also: if you're building profiles yourself using the Lens Profile Creator ... the idea that your target has to be uniformly lit is often stated, but false. It is true that you need the lighting to be consistent from shot to shot within an image set, but it does not have to be uniform across the chart. In case you are wondering at the technical level how LPC can possibly build a vignette compensation routine from an unevenly lit chart -- remember that you are supplying multiple images for a given optical configuration to LPC (usually five to nine), so LPC can apply a sophisticated algorithm to reconstruct the realtive illumination function of the lens by studying all the images together (not just a single image).
Hope this helps.