I know that. It happens on my local wamp-server (not on my productionserver). I have a solution, but it's very much automated in my mind, so I'm not sure which one it actually is. Try one of these:
- restarting your (wamp)-server (provided your working on a local (test)server or have access to your server)
- refreshing your myURL/admin
- running a /dev/build (not very likely that will work though)

2. Yeah, refreshing browser while you're in admin
3. check with your hostingprovider if their server-setup is OK. Server-sequirements of SS are for example a memory-limit of 32 MB (a little bit below that should also work in my experience, but not to much of course. Maybe it's possible to bypass the server-setup as suggested here.
4. If nothing works, still: check with your hostingprovider and explain them js isn't working well. Maybe they know something?

Unfortunately I don't have any further suggestions. For me: everything that worked badly on my local wamp-installation went fine as soon as I put my site online, so I'm pretty convinced it's in the server and not in SS. Please let us know however if some (or none) of these worked for you.