You are probably running OS X correct? Apple comandeered this keyboard shortcut for an OS shortcut to "Search with Google" in Safari. If you want your shortcut to work in InDesign, simply go to System Preferences > Keyboard > Shorcuts and click on the Services option on the left. Now look in the right column and you'll find the search for google optioin with a checkmark next to it. Uncheck that option and your shortcut should now work in InDesign.