Changing old fixture to hampton bay ceiling mount. After connecting the red wire from the switch to the wrong connection, re-did connetion, breaker tripped when the light switch turns off. Redid connection again, making sure everything was connected, light is on, no breaker tripping, but light will not turn off unless the bulb is unscrewed - switch does not turn light off. Help!

Red wire, so is there a sceond switch also controlling this light, a 3 way

There are 2 switches, but only one has worked as long as I have been in the house. Neither switch works now.

Replace switch? Can I replace from a 3 way to a single?

My suggestion is that we fix both switches. Start by buying 2 new 3 way switches. Let us know when you are ready to start replacing.

I'll grab them, but if the other switch, which is in the same box, is a 'ghost' switch - doesn't work anything - can I wire nut off the wires and just run a single?

Red wire and second switch do not say 'Ghost" switch to me, says bad 3 way. Switching to single is not impossible but one or both of your old 3 ways is shot, here is how the traveler line works. Power enters the fisrt switch and always exits via one of the two other wires. One wire goes to the light and the other travels to the other switch. Your choice is turn on the light or send power to the other switch, 2nd switch operates the same with the same choices.

Your "ghost switch" may control half of an outlet.
Or it was wired for separate Light and Fan.

Sorry Bob but I have to take exception to your explanation of 3-way switches.

The power enters the first 3-way switch via the common screw or terminal. It exits that switch by one of the traveler terminals. There is always a connection between the common and one of the traveler terminals. One of the traveler wires is always energized. Which one depends on the switch setting. Both traveler wires go to the second 3-way switch. Power enters the second switch by one of the traveler terminals and exits out the common terminal which is connected to the fixture.
If the common of both switches are connected to the same traveler the light burns. If the common of the second switch is not connected to the traveler that has been energized by first switch the light does not burn.

The switch only powers the light - there is nothing else for the switch to power, thus the question why there are 2 switches on this plate. I only need 1, as it's the only light in the room. The washer & dryer are on a different circuit, as are the furnace and hot water heater. The kitchen lights run off this circuit, but are not controlled by this switch - the switches are not located anywhere near each other. The wires into the switch are hot; it's just ironic that the switch ceased working at the exact time the fixture was changed.

May control half of an outlet.
Or it was wired for separate Light and Fan.

it's in the laundry room - just the light. Small room - 6x8

I would try the red again, must have been pinched.