A little late to the game, but my XB321HK has gotten a bit of dust between what looks like the LCD and the screen. No amount of gentle tapping or suction cupping has dislodged it. Wouldn't be a huge issue, but the speck has gotten stuck right in the middle of the screen. Otherwise, it's a superb monitor probably the best I've used, but I can't live with her like this (it's like my favorite horse has a limp).
My display is unfortunately out of warranty at this point, so I'm looking at taking the display apart myself to dislodge the speck. Has anyone tried taking their screen apart? Is the disassembly similar to other displays?
Edit: Good news, and very bad news... I was able to remove the spec (it was a large piece of something/dusk that had somehow stuck itself to the back of the LCD panel (between the LCD panel and diffuser). In the process, I cracked the bottom-right of the LCD panel and the screen now has flashing lines in the top-right of the screen. The LCD panel rests on a few plastic hinges on the bottom and I guess it cracked when I was moving the panel forward to clean. Fuuuudge... I guess I'm in the market for sourcing a new M320QAN01.0 panel. These things happen I guess, and I take comfort in that I was at my wits end with the spec stuck right in the middle of the screen.