I don't use a preset to adjust the curve. I only use my presets when I'm making a variation of chrome or other metallic finish. This is the drop down menu where I have saved all my presets. I assume this is the menu you are referring to.
You probably already know this but it bears repeating for those that don't. Just place your cursor in the very middle of the curves dialog and just click and hold to drag the line at a 45 degree towards the top left corner a little bit until you like it. You can also create any kind of curve you like and if you want to save it, you have to click on the little plus icon just to the right of the drop down menu at the top, then just name your curve preset and click OK.

Are you saying that you already have some saved presets and now they are not showing up? Is that the issue?