InDesign shortcuts won't function

You say, "as soon as I click ok, an error occurs"

If you get an error dialog box, can you please post it.?

As @Bill Silbert points out, please tell us what operating system (exactly) you're running and  (exactly) what InDesign version you're using. Often there are incompatibilties which can cause crashes which are not obvious without knowing about your system.

Also, does this just happen with one particular file? Does it happen with other files as well?

What operating system and what exact version of InDesign are you using? Make sure that both the OS and InDesign are at their newest versions as there have been compatibility issues recently on the Mac.

As far as missing keyboard shortcuts it could be that you have other programs or plug-ins running that may be using the same shortcuts. Try rebooting your computer and only open InDesign. If the keyboard shortcuts work with no other programs launched then you will have to open the other apps one at a time in order to see where the conflict lies. 

However, since you mentioned that you are getting crashes when you try to change the shortcuts it actually seems more likely that you are dealing with program corruption. In that case it would be a good idea to try trashing your InDesign preferences. This will reset the program to its defaults which usually will fix operational issues.

To do so:

For Macintosh Users: The User Library folder in which InDesign’s preferences are stored is hidden by default on most Macintoshes. To access it make sure that InDesign is closed and click on the desktop to launch a Finder Window (Command-N). With this window in column view follow the path User>Home folder (it’s the folder with an icon that looks like a house—it may have the user’s name rather than “Home”) and click on the Home folder. With the Option Key pressed choose Library from the Finder Go Menu. “Library” will now appear within the Home folder. Within the Library folder find the folder called Preferences and within it find the folder called “Adobe InDesign” and the file called “com.adobe.InDesign.plist” and delete both that folder and that file. When InDesign is next launched it will create new preference files and the program will be restored to its defaults.

For Windows Users: You can try the quick way of resetting on a PC which is to hold down Ctrl + Alt + Shift when launching InDesign and respond affirmatively when asked if you want to reset. There have been some recent reports that the window asking if you want to reset is not popping up but that the prefs are being reset anyway. If this works great but if it doesn’t you may have to manually delete them.

To do so: On Windows 7 and above the preference files are hidden. To find them go to the Control Panel and open Folder Options and then click the View tab. Then select “Show hidden files and folders” or “Show hidden files, folders or drive options” in Advanced Settings. Then delete (or rename) the folder at the end of this path: C:\Users\<USER>\AppData\Roaming\Adobe\InDesign\<Version #>\<Language>. Make sure that InDesign is closed when you do this. When you relaunch the program it will create new preference files and the program will be at its default settings.

The advantage of manually deleting preference files is that after you’ve reset up the program (make sure that no document window is open) to your liking, you can create copies of your personalized “mint” preference files (make sure that you quit the program before copying them—that finalizes your customization) and use them in the future to replace any corrupt versions you may need to delete.