P: Unable to enter information into the output of curves

I am using LAB and curves to do some color matching with images and have run into a strange problem. It should be noted that I have been working on a ton of images over the last few days using the same method and haven't had this problem before. This is the first time I have tried to do this since updating Photoshop this morning. I'm also using the most recent version. 
I make my selection that I wish to alter and create a curves adjustment layer. Shift+Ctrl click on the second color selection. With that color point selected in the curves dialogue box, I click on output to change the number but the box disappears. I then click that point again to select it, the box appears again, and when I click the box to type in a number the box disappears again. 
I have already restarted my computer, reset the preferences, tried another file, and cursed. 
I'd greatly appreciate some help or ideas. Thanks!