If someone jostled your lava lamp, you may now have a cloudy mess. This is the big reason that manufacturers and lava lamp aficionados advise not to turn your lamp upside down or shake it. Once your lamp becomes cloudy, it may be impossible to fix it without opening it up. This voids your warranty, which is why you should try other approaches first.
Turn off your lamp for two hours so the wax fully cools. Then turn it back on. As soon as the water starts clouding up again, turn it off to cool for another two hours. Keep doing this---for a week if necessary. If after four to six cycles or working on it for a week doesn't clear up the water, move on to the next Step 2.
Run the lamp for 10 hours. This move is based on the possibility that the lava isn't warming up enough. If this doesn't cure the cloudiness, then move on to Step 3.
Unplug the lamp and let it cool for two hours. Unscrew the cap and pour out the liquid. The wax should be solid after two hours of cooling, so there shouldn't be any risk that it will pour out.
Pour chilled distilled water into the globe to rinse the sides. Try to pour along the inside wall of the glass to get rid of any residue that would contribute to clouding. Do not pour the water directly onto the wax lava at the bottom of the globe. Do not swirl the water or shake the glass. Pour out this water and repeat this rinsing process once more.
Fill the bottle with distilled water so the level is 2 inches from the top of the bottle. That air gap is important for the lava's functionality. Again, pour the water onto the side of the bottle, not directly onto the lava.
Turn the lamp on again. Don't put the cap on again just yet. You want to heat the lava at this point to see how much salt you need to add to get it to flow right.
Let the lava warm up for an hour. Then prepare the salt solution. Fill a drinking glass with hot distilled water. Dissolve as much Epsom salts or pickling salt (which lacks the iodization that can muck up the water) in it as you can.
Wait until the lava starts rising a little from the flat shape when it's cold, and dip one inch of the straw into the salt solution. Put your thumb on the other end of the straw, carry the water over to the lamp and gently drop that inch of water into the lamp. Don't stir!
Wait 10 minutes for the salt to disperse on its own. Never mix the salt into the water. If after 10 minutes the water isn't dense enough to force any lava up to the top of the bottle, add another inch of solution. Keep doing this every 10 minutes until the first bit of lava travels close to the top of the bottle. The water is now just dense enough to get the lava flowing right.
Add one drop of liquid dishwashing detergent to increase the surface tension of the wax. This gets the large blob to break up into smaller blobs. Add two drops of food colouring to match the water to the colour of the lava. Screw the top back on and you're done.