Marking this as tbd as it's unlikely to land in 1.6.x (since it doesn't sound like something that would be a 1.6-introduced regression). I'd be curious whether this same problem is reproducible on 1.7, given the new loader.
Moreover, not sure how much priority this will be given, given that a server returning a 200 in a 404 case certainly seems like invalid behavior beyond our control. The fact that it's causing further issue on FF7 is interesting though...
I am not a loader expert, but it seems to me that try/catching that line of code might hamper error reporting in cases where you really do want the loader to inform you of a problem when attempting to execute code in a loaded module, and I also can't imagine it'd be at all good from a performance standpoint either.