>If I, a reasonably intelligent moviegoer, can't decipher a
>film, then why would that be my fault? There's a huge
>difference between a movie that makes one think and a movie
>that makes one's head hurt.

Thats sort of a personal thing though. Something incomprehensible to you could connect with someone else on multiple levels.
It's up to you if you want to delve deeper or decide there's nothing to delve into.
Even if it isn't apparent to you the meaning of what you're seeing, it doesn't mean that the filmmaker isn't expressing an idea in a way he/she sees fit, or that there isn't real meaning to the film.
& if you find the content incomprehensible, can the film still be great on other merits? does the way it's made, shot, directed, acted, look, FEEL factor in at all????

But,
If it makes your head hurt to watch it, for the sake of your health, stop watching it!

Since someone brought him up, in the case of David Lynch, a film like Inland Empire I have absolutely no idea what his personal meaning of that story is.
So it makes it sort of "incomprehensible" in my case, because I couldn't sit here and write an analysis of it that made sense to anyone but me.
But I certainly wouldn't dismiss that film. It's obviously a personal vision/idea and there's a ton of messages in it that make your mind wander. You could have an hour long conversation about it and the people involved would still not really know exactly what it means in the end. but it still evoked personal thoughts about what you've seen & lead to conversation about things that might not have entered your mind otherwise. Things you wouldn't normally be shown in your more straight forward films
It's great film making & if certain people don't fully comprehend it (including myself) that's irrelevant to that fact. (in my own opinion)
Of course the "average moviegoer" (that sounds stupid but I think you know what I mean) these days would immediately write it off, but if that's your style, what are you doing even watching David Lynch films? lol
In the case of Mulholland Drive I think I could walk you through it if you wanted to. I certainly think there's a concrete answer to that film that's not really hard to follow once it clicks with you.