I doubt that this is a serious post. Newly registered person with implausible situation.

I don't think it's that far fetched.

Connect the two black wires together and run them to one side of the split receptacle. Connect the red to the other.

I suspect you have

Black IN - unswitched power feed in
Red IN - switched power feed in
Black OUT - unswitched out to the next receptacle.

That's all consistent with the behavior of the two things you've tried so far.

Why do you think it's implausible? Is there no combination of wires in this situation that could result in the symptoms he's describing? Maybe there is just something wrong with the description?

What cables are coming into the box? Which cable is supplying power? It sounds to me like there are there two cables (one black/white, the other black/white/red). Is that right?

I'm assuming you didn't note how the old receptacle was hooked up?

When you say ONE ground, do you mean that there is only one ground going to the receptacle, but there are more grounds that are all connected together and tucked back into the box?

Edit: I didn't see ron's post before I replied. He's probably right.

This post was edited by greg_2010 on Thu, May 9, 13 at 9:22

Nothing in the post about how the connections were originally-- but some detail about how the connections are to the (supposed) new receptacle. Why would one be unconcerned about the original hookup and very detailed about the new? Why would one alter connections and expect the same results?

A lot of people just pull things apart and then go "Oh sh@#!"

OP here. Yes, this is a real problem I am having. I switched out all the receptacles in my house (27 of them) and this is the only one I've noticed a problem on. I'm a new home owner with no electrical experience, but after changing a few without any issues, I thought they would all be easy.

I've attached a picture to make things a bit more clear.

most likely the red is a switched leg. One black probably constant hot and the other black feeds other outlets.
Between the two brass screws is a tab that connects the two hots. If you break off the tab it will split the outlet so on is switched the other is not. So the two backs should be on one screws and the red on the other. Test it with a volt meter first

thanks for the responses guys. i switched both black wires to the same screw and the red to it's own and everything is working. i learned my lesson that i shouldn't just blindly connect wires without really understanding what each wire is for.

You didn't put both wires under the same screw, right? That's not allowed and will probably come loose in the future.

Use a wire nut to combine the two wires and a pigtail to connect to the screw.