What really caused Ashes Meltdown in Alien?

Interesting theory! But then again, why didn't David malfunction when Vickers pushed him up against the wall in Prometheus? 

I think Ripley's attack made her a threat that needed to be eliminated as per his orders rather than a fault in his processing.  He wasn't 'damaged' when he was talking to them later on (aside from that bit about his head being knocked off).

Ripley did damage him, because Ash starts bleeding down the side of his forehead (just before he snatches her hair). But I'd concur that that didn't make him berserk, rather triggered a different path in his programming logic, which told him Ripley must be eliminated. You see he returned to a relaxed state when he was atop a table, decapitated.

I think his orders told him to kill her, rather than any programming or error in programming.

I often find some people (in general; no one specific) get hung up on 'well so and so could have programmed this or that android'. No need to go to that trouble if you can just give them a verbal or written order to follow.

Interesting that the chip is not installed in a less vulnerable space like in the chest cavity. That could problematic though to access it if needed.

dk, At the same time when you watch where the processor is absorbed into the head (walter video) looks like it goes in the top in the video not at the back near the base.

Alex, where Mere pushes David hits in a different location near where the crest of occipital bone is.  Ash was struck closer to where the occipital condyl is located.  Human anatomy of course not android.

Thanks Stan, the white blood (milk) if you will ran down his forehead which happens right after him and Ripley have that confrontation in the communications room which is what made me think about Ash being damaged from the blow at the base of his skull when she pushed him against the wall.

I also thin S.M is right to a point.  I know SO-937 said crew expendable but at that point they hadn't made it a point to blow up the ship until after they torch Ash so she wasn't really a threat to him or the specimen.  Well maybe when she pushed him into the wall, but that was more of a desperate reaction than a threat.  I mean that was really creepy him silently sneaking in and looking over her shoulder and then speaking at the last second.  How did he get into the room without the door making any noise. (really?)

You do have a good theory there however... you have to take ALIENS for canon, and I just don't. James Cameron had his own ideas and while I did enjoy the product he put out I believe he watered down the ALIENS. My reasons why are my own personal preferences. He got rid of the awesome "domes", he never explored the "eggmorphing" which was pretty terrifying considering that was what he was going for??? And... he turned them into bugs??? If Giger or Ridley didn't have anything to do with it then for me anyway it's just another in the series but I don't consider it canon. For now it's PROMETHEUS, ALIEN: COVENANT and ALIEN. That's it. I hope Ridley has six more in him. Fingers crossed!   

I think the yoghurt dripping down the head of Ash and his brief indecipherable mumbling in that scene sort of reveals that it was at least partly a malfunction that lead to him attacking Ripley.

I think Ash attacking was either a standard safety-mechanism when the chassis (specifically the head) had sustained enough damage intentionally caused by humans (wasn't this a flawed unit?) or a specific objective (independent or programmed) that was triggered after the shove impact to kill the main threat: Ripley.

Well, in aliens : out of the shadows ash downloaded himself into the nostromo'so computer before his confrontation with ripley which could have effected his robotic body to malfunction

Shasta, I'm not sure if Lebbons book is considered canon.  I know the movie novelizations are.  I'm not trying to take anything away from Tim.  I hear his books are really good, but I can't accept that.

"How did he get into the room without the door making any noise. (really?)"

He used his 'not giving away the surprise Ninja android skillz'.

S.M - LOL, ok he must have been really good.  I mean to get into the room you have to play 10 minutes of PONG, play tick-tack-toe on the keyboard, then pull the slot machine lever to get in.

How did he get into the room without the door making any noise. (really?)

I think that was an actual oversight.

No, it was deliberate to not give away the surprise.  If you look very closely you can see the light change very briefly behind Ripley to indicate the door opening and closing, but as Ripley is so focused on the computer she doesn't hear it and so we as the audience can't hear it.

Hmm.. I had read it was a mistake. I can see how Ripley would not have heard the door but as a viewer, I would have expected to. I never even noticed until a blooper site mentioned it. Maybe some one could do a cut and have a door open that sounds like the Star Trek OS door!

It could technically be a mistake, since the door obviously makes noise, but if you had it make noise in this scene it would ruin it since Ash enters before Mother displays the 'Crew expendable' payoff.

The scene is shot with close ups on Ripley, the keyboard and the screen, so we're focused tightly on those things, so cinematically you can get away with deliberately leaving out the sound effect.

S.M even if we're focused tightly on what she is doing the problem is we're in the forest when the tree falls.

Not sure what you're saying.

S.M no quotes this time....really?  (poke poke, lol)

If a tree falls in the forest and nobody's there, does it make a sound?