[jfrancho]

By "label," I'm sure the OP is referring to the color labels for sorting. You cannot change metadata while the file is open. Click Done in ACR, and return to Bridge to change IPTC, label, or rating values. The sheet of paper indicates that a document is open and locked for editing. If there are no open documents, then one of two things are happening: you are in the process of converting that raw to another format, or there is a file hung in ACR. For the latter, open another raw file, and click Done, and that should release it.