So it appears that the same problems that are preventing .mod sound files to play in some versions, may also be causing or related to the problems with Call of Duty Black Ops.
I've tested the standard 249 versions of: cfg60, cfg61a, cfg61a2, cfg61a3, cfg61b, cfg61b2, cfg61t1, and cfg61t2.
As with the .mod sound file issue, only cfg60 and cfg61t1 are working properly for this situation.
With cfg60 and cfg61t1, I'm able to play all modes (singleplayer, mutiplayer, zombie) fine with the following configuations:
CFG = cIOSx 249 v20 base 57 | Game = cIOSx 249 v20 base 57
CFG = cIOSx 249 v20 base 56 | Game = cIOSx 250 v20 base 57
CFG = cIOSx 249 v20 base 56 | Game = Hermes cIOS 224 v5.1 base 57
CFG = cIOSx 249 v20 base 56 | Game = Hermes cIOS 223 v5.1 base 57
Using anything other than cfg60 or cfg61t1 and the above combinations, singleplayer works, but the other two modes don't load.
Hopefully this will be helpful to the devs and to others having trouble with the game.
* I did not test with CFG-222 versions, versions under v60, or other versions of Waninkoko or Hermes installers besides what's listed above.