Here is my experience with COD5 on Wii.
First I had a patched copy of the PAL version. I installed Waninkoko's 0.1 Loader and got the game to run on that, albeit with choppy cut scenes and sound, but it was playable. Online was far too laggy with constant reading of the disc seemingly slowing the game down making it unplayable.
I might add, I have a NTSC unmodded Wii.
I knew on the 0.3 beta the PAL version never worked, however, I heard that a 1:1 NTSC version does work on 0.3 beta Loader. So I now have a 1:1 NTSC copy of COD5 and I can play it on either 0.3beta or the new Gamma. oftchip r43 yet but I think it will work on that too.
I think some people are having issues by uninstalling the wrong cIOS's over old ones or what order they do this in. For instance, I took my SD card with all my loaders and stuff to my brother house tonight so he could have the stuff on his Wii.
I deleted his channels to begin. I then pressumed he had his 0.1 loader installed on rev5 at 247, which I was wrong and it was actually revt5 at 249. My mistake here. So when I installed the new cIOS rev7 at 249 things should have been fine. But where I went wrong was I then checked my WADs and uninstalled cIOS rev5 pointing at 249. So what happened was my cIOS at 249 for both was deleted.
I loaded up the game and it was doing the error. I was a little confused, but after retracing my steps and checking with ATD, I realised my error.
So I went back in and re-installed cIOS rev7 to 249, and hey presto, it now works perfectly.
So my point is this. There may be other issues, but I suggest taking everything off from the old loader, any channels and cIOS's associated with them, so use ATD and delete 249 and 247. Then install the new cIOS rev7 which automatically is at 249. Install any channel for the loader if you want, and use default loading. I have had no problems doing this.
I think a lot of people are over complicating it for themselves and just need to do the basics to get going. Then once your up and running, then try adding fancy channels and graphics and loading from main menus with menuloader ect.