We've had this error before (I think we've had every error conceivable), but I cannot recall exactly how we fixed it. We may have reloaded the libraries from the teamwork menu, or it may have fixed itself. It obviously wasn't a big enough issue (compared to the others) for me to remember.
Have you updated to the latest hotfix - 3862?
If so, I would export out all custom parts from the embedded library, then delete the from the library, then add them back one by one, sending and receiving each time. Or do that in reverse - start removing them and send/receive until you find which one is causing the problem. Either way - export them first! That way you can be more selective - chances are you have an idea of which one it may be.
Once you find it you can decide whether to delete it or fix it somehow.
Keep in mind that if you have hotlink modules, the issue could be compounded through your hotlink libraries.
Cheers,
Link.