My Samsung 305T plus started flickering in a weirdly regular pattern.
My first guess was that it was the graphics cards, as the pattern did not show when the cable was disconnected (and the monitor cycles through solid colours).
I needed to use the screen today, so I purchased a new cheap, silent Radeon graphics card, plugged it in, and ... no cigar, still flickering.
After searching some more, I realized that this is a common problem with this type of monitor. People have been fixing it by baking electronics, having the soldering refurbished, changing capacitors, and what have you.
To drive it, I also needed a new graphics card, so I ended up buying a more expensive Radeon card along with the monitor. A minus is that it has fans - two. (I don't think I have bought two graphics cards on the same day before.)
Plugging in the new(est) graphics card didn't work - it seems like it isn't there at all.
Looking closer, I realized that it has a socket to plug a power cable into. A 6 pin PCI express power cable. Something my (nice, silent fanless) power supply does not provide.
So I can drive the monitor in 1920x1080 with the old(er) graphics card, until I get a molex to PCI express 6 pin cable. sigh
Update: Looking for a power cable like this... Jeez. You can order one that cost you 178 DKK, one that costs 123 DKK, one at 50 DKK, or you can go to Brinck Elektronik, where there is a queue on a Saturday afternoon, but the cable is in stock, and it costs 24 DKK, a whopping 2-7+x less.
First impression of 3840x2160@60 Hz on a 28" screen (which, by the way, just worked automatically with Debian unstable and a displayport cable): I need to adjust fontsizes and configure Firefox and Chromium to scale up (same as on the 3200x1800 screen on the laptop). A 32" would be nicer, but this will do.