curves are not actions* and should therefore be loaded differently:
hit ctrl + m while on photoshop to bring up the curves window (or go to image > adjustments > curves), click on the tiny button between the drop-down menu ("default") and the OK button and choose "load preset" - and locate the curves from your hard drive. photoshop curves have the .acv extension.
my curves are usually named after countries or cities. please do not redistribute (but rather link back to this blog so that i can keep an eye on the downloads) but feel free to use them in your creations (no link back needed, since it's just colours). however i would love to see what you do with them!
extra: if you would like to keep the curves there permanently, just save them to the folder C:\Program Files\Adobe\Adobe Photoshop CS4\Presets\Curves (or whatever version of photoshop you have). this way they'll be always loaded and ready to use.
* why i prefer curves: they are much less destructible than actions and you can still customize them according to your original picture, plus they load super fast (unlike actions which may sometimes take a minute to complete!).