Lightroom is completely self-contained and doesn't need any other software to work. I've used it from V1.0 right up to the current 2.6 and have imported raw files from six different Canon cameras that I own and other raw files downloaded from the net. I have never seen anything like the problem here. I suggest reinstalling Lightroom.
As for Zoombrowser, it used to have Raw Image Task integrated into it but that was withdrawn over a year ago, I think with the release that accompanied the 50D. Now, if you want to use Canon's software to process raw files you need to install DPP. Zoombrowser can link out to DPP but I just go straight to DPP if I want to use that software.