[Captivate General] snoboarder071:
If your button is broken, your button is broken. Sorry :(. Some people have had luck cleaning it with electrical cleaner but unfortunately I was not one of them. Eventually, you will probably want to send it in somewhere to get fixed (you need all three hardware buttons for various development functions). But if you are like me and you just need a temporary fix (I'm happy w/ my current rom and will be upgrading soon), then read on!

So what you are going to want to do is swap your power and volume up functions by remapping their respected buttons. Alternatively, you could swap your power and your volume down, but I think it's more important to be able to turn it down (plus you can still take screen shots in ICS).

Here's how you do it:

You will need a file explorer (and phone for that matter) with root access. ES File Explorer would be my personal recommendation. Make sure you have root access turned on in the settings

You will probably start in /sdcard/. Navigate up one folder then go to /system/usr/keylayout. Here you will find all the files that control your buttons

For the physical buttons, go to "aries-keypad.kl" and open as a text in a text editor that your file explorer hopefully came with (if you can't in yours, use ES File Explorer)

Write down or take a screen shot of what you see so you always have a reference of what it should look like and won't need to keep checking here :D key 114 = vol down, key 115 = vol up, & key 116 = pow

Cut and paste POWER WAKE to key 115 and VOLUME_UP WAKE to key 116

Hit back to leave and save the file when prompted

Reboot your phone. You'll probably need to pull the battery since your power button is toast

That should do it. Your volume up button should now control your power and your power button should now control your volume up. A couple (not so important) notes:

I think you can accomplish the same thing by switching the key numbers and leave the functions where they are, but can't be sure since I didn't try it

If your button is behaving erratic and going off without you pressing it, completely erase the key and it's function from the file. After I used an electric cleaner on the button this happened to me. I tried leaving the key in there and assigning it no function but my phone went bonkers.

I have no idea if the number of spaces between the various functions and WAKE are of any significance lol. I would guess not but I kept them the same to be safe.

Some people may want to assign the search button as volume up. I'm guessing you could do it the same way but again, I haven't tried. The file cypress-touchkey.kl also has softkey functions but I'm not sure if you would need to play around in that one instead or possibly do both. If anyone has had success with this please share!

After editing the aries file, I notice a duplicate in there after reboot that has the old setup. In the file explorer it has the same name, but upon opening it, I can see that it is a .bak file. I'm 99% sure this is a backup that ES File Explorer has made for idiots like me that shouldn't be playing around in these files and need to revert :o

OK that's it. Sorry this got so wordy. I hope this helps someone! :)

Credit for getting me started: http://xdaforums.com/showthread.php?t=1325867