I notice that very often responders to "help, help, my FS2 is broke!" posts assume that the issue is not the most obvious thing that could cause the sort of problem described.
"Help, <list of things that happens when launcher flag X is used/not used> is happening and it's icky, wtf?"
"Help, <list of things that happen when you don't have a mod.ini, or are trying to play a campaign without the right mod active>"
"Help, <list of things that indicates you're playing retail>"
Although a lot of this stuff is covered (I think) in the (stickied) FAQ, problem is people will not always have looked there. Heck, people often don't even come here, they just spam General FreeSpace Discussion with support questions.
Note: I think Lobo has figured this out, hence his insane problem-solving skills
Just a suggestion, consider the 'incredibly dumb mistakes' before thinking about the vagueries and intricacies that have an off-chance of messing something up for advanced modders. Take context into account - is this someone who usually knows what he/she is doing, or does it seem like they haven't got a clue what they're doing? I'm not saying we should treat new members like idiots, but (especially considering the increase in publicity we've gotten in past months), it's not really safe to assume they are aware of "obvious" problems.