Dust under the screen,

The most severe problem dust can cause in an LCD TV is a short circuit. This occurs when dust enters the television's casing and settles on one or more of the internal circuit boards. Enough dust can cause a short circuit, which will prevent the TV from working at all. In other cases, it will damage picture quality or prevent certain features from working properly.

Because a short circuit can only occur when enough dust is present inside the TV, this problem happens after the TV has been in use for a number of years, meaning that it will not be covered under the manufacturer's warranty. In many cases of short circuits, repair is expensive, and you are better off buying a new set.

Image Quality

Dust can also have an effect on an LCD TV's picture quality without entering the LCD's casing. Dust that settles on the surface can distort the picture and decrease its brightness. While it's easy to wipe the dust away, use only a soft cloth and mild cleaning solution to avoid scratching the screen or causing permanent damage with caustic cleansers.

Dust under the screen can be more difficult to clean. Using compressed air to blow the dust out is the best option, short of disassembling the set to clean the screen from the inside. Keeping the surface of the screen free of dust is usually sufficient to prevent dust from getting under the screen.

Control Problems

Another effect dust can have on a an LCD TV occurs when it enters the space around buttons, making it difficult to control the television. On certain sets, dust will cause buttons to stick or prevent them from engaging when pressed. Using compressed air to blow the dust out, or resorting to using only the remote control, will solve this problem.

I had this problem before, i took a my household vacuum to all the vents on the unit and it freed the dust up. if your vac is very prowerful you may what to muffel it some how.

2 possibilities: -Wipe/clean key pad NO WATER,dirt dust moisture affecting key function -Low battery charge so reboot/Hold keys down till screen goes blank. Then removing battery clean contacts on battery itself and phone battery metal tabs carful they are very fragile break easily that happens phone will need to be replaced/refurbished etc.Full charge downside phone can't be used for awhile

Check that the filters are completely clear and not blocked - especially the top filter on top of the bin assembly. If its clogged completely brush it free of dirt and then reassemble. Make sure the inner cone filter and mesh filter is also completely clean. Then check the hose and main dust channel - something is clogged that makes this machine overheat and stop working - and often with this model (Hoover also make it in the UK under the Alyx name) its down to clogged filters or small clogs of dust in the dust channels. 
Don't forget to rate, thanks.

Hold the camera upside down and gently blow off any grit and lose dust particles. Next lightly wipe the lens with a few drops of lens cleaning fluid, place the fluid on the lens cleaning paper, not directly onto the lens and then wipe the lens.

Hi,
looks like your touch screen is faulty . it could just be dust / dirt under the edges of the screen. If dust is trapped under the edge , it can effectivly be pressing the screen a little causing letetr to change or dissapear. See if you can get to clean under and around the edges , if the cleanup doesn't work then most likely cause is a faulty touch screen which will need replacing. Good luck.

take off the screen cover (the plastic) with a pin and clean it with a (magic) cloth.

Well, I pretty much knew that the display would have to be disassembled to clean the dust out. I should have been more specific by asking if the display "could" be taken apart to clean it out, especially since the dust is in between the image and light source layers.