All of a sudden there is no hot water pressure on any faucets in the house. All cold water faucets have pressure.

You have your work cut out for you. Sounds like every hot water faucet is clogged with mineral built up in your water heater due to not flushing it on a regular schedule. Now the mineral's in your system and is clogging the inlet ports and the seats of your faucets. The solution would be to open up each faucet and check and clean the hot side of the valve. Before you reassemble turn the hot water back on for a minute to flush out the hot water supply. Also you need to start flushing your heater. For long life and fewer troubles you should keep your heater clear of mineral build-up by flushing on a regular schedule. Let me show you how. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures. Don't forget to flush it out every month. Your heater will thank you for it. Good luck, Tom