Seems my question has been missed, and I'l still having issues with this. It seems like a common problem too.

It's my first Dell product, and so far I'm certainly not impressed. Considering returning them and going with the Asus ones I was looking at instead... It'd be a shame as they have a thicker bezel, but at least they work.

Chris; be honest - have you seen ANYONE who has successfully got MST working, reliably and flawlessly?
Maybe you should grab a couple of these from the warehouse and try it out yourself. It's quite clearly a fault in the product, not a fault with our systems; it's happening to everyone who uses MST regardless of setup; even my friend with a nVidia card gets it.

I should clarify I mean that once they got it working, they can stop and start it at will. My setup is working right now, but I can't use any other ports on the monitor or it kills it again; which means I can't use my HDMI devices like I originally planned.

Alright; now can you safely switch to using another HDMI device on the second screen and switch back hassle-free? My screens themselves work after a lot of tinkering; but I can't switch inputs without having to set it all up again.
If so it might be worth filming a small tutorial on setting up; wipe the installation from the PC so no drivers are initially there and people can see it from the start, maybe we are all missing something key.

It'd also be interesting to see how it works on a non-Dell machine - it seems almost everyone posting is using a custom build (Which is quite common amongst us multi-screeners), so maybe there's some low-lying software compatability which just means it works easier on a Dell than on other machines. Even just trying with a retail Windows (instead of the Dell OEM one) might throw up something useful?

Looks like they're one step ahead of us on that front. The only way to do anything with your warranty is with the service tag, and funnily enough, these monitors seem to be missing that.

The detection tool which they offered returned an invalid code too. Let's just hope they reply to this soon with info on how to return both of these £200 doorstops so I can just get rid of them.

It's a shame, if they actually did come up with a solution I had money aside to buy a third. They've effectively lost out on £600 from me now, all because of poor support & bad quality control.

I'm assuming we've all had these monitors less than a year?

Here's an idea; to get there attention we'll all just send 'em back. By law they have to refund us as the monitors are clearly not fit for purpose. If we just all send them back (to DELL, not wherever you bought them from), maybe they'll finally realize there IS a problem instead of just trying to palm us off with "well it works for us using Dell hardware and Dell OEM operating systems..."

These monitors need to be taken off the market before they claim more victims.

Looks like Dell has abandoned this thread.

Does that mean they finally admit there is a factory fault with this product?

They won't of tested it with anything that isn't made by Dell. That's their flaw- it works with their own system and OEM software so clearly that means it absolutely must work on everything. I invite any dell rep to come to my house and take a look for themselves. If they can consistently switch it between HDMI on one machine and DP from another without issues, then I'll buy a third monitor on the spot.

Mine has actually been alright recently but just went again this morning.

Dell, this is RIDICULOUS. It's also fairly clear that you are just ignoring this thread now - which I assume means you know about the problem but refuse to acknowledge it.