Fijim,
I would be surprised if your two cameras have the same sensor. RAW files are essentially streams of electrical measurements from your cameras sensors. Every different sensor (I.e., Canon 7d versus Canon 30D versus Nikon D70) has different characteristics, so every sensor needs special software to decode it into RGB to save in a picture file.
Just because Mac OS could decode your 30D does not in any imply it will be able to decode your 7D (unless, of course, Canon built those two cameras with the same exact sensors).
The fact that they both produce CR2 files is inconsequential. That file is a for that C developed to store its newer RAW data. Each camera still needs special software to interpret that CR2 (or NEF in the case of the Nikon). Have you ever used Microsoft Word? Have you ever received a .doc file that your version of Word said was made with a different version of Word, and therefore might not be loaded correctly? Same thing with CR2 files. It's the same file extension, and the same file format, but you still need the right software to load it.
Can you still view your Canon 30D pictures? If so, your problem description is a bit misleading.
Do you have Apple Digital Camera RAW 2.7? It appears you need that for the 7D.
http://support.apple.com/kb/HT1475
Kathleen, I'm not sure about your problem. I can't find the Mac OS 10.4 RAW update page. I'm not sure if it's the same as the page I pasted above.
nathan