I've been using a great iPhone clipboard app by Tapbots called Pastebot for a few years now. It's a little copy/paste utility that stores and edits stuff you've copied using your iPhone or iPod touch. But the best feature of the app was always that it could copy and paste to and from your Mac using a secondary app called Pastebot Sync.
With the introduction Mountain Lion, Pastebot Sync stopped working for me. Every time I wanted to use it, I had to open the preference pane and turn it back on. After not getting much of a reply from the good people at Tapbots when I asked about it via Twitter (hey, they've been busy!), I just figured it had been abandoned. Not so. Here's how to fix it.
The problem is with Apple's Gatekeeper, a new feature designed to protect casual users from potentially harmful apps from untrusted developers. (More details in that link if you care.) The problem is that you can't bypass Gatekeeper for Pastebot Sync if it was already installed when you upgraded from Lion or Snow Leopard.
Go to System Preferences, and right-click on the Pastebot Sync icon. Choose Remove "Pastebot Sync" Preference Pane. Once it's gone, redownload it from the Tapbots website. After downloading the .dmg file, double-click it to mount the disk image. Then you'll see the Pastebot Sync icon; open it by right-clicking and choosing "Open" rather than by double-clicking it. This tells Gatekeeper that you want to allow the app to open even though it's not approved as safe. (You can ignore the warnings that may pop up about this; the app is indeed safe.) You should be good to go now!