When I call SecureSocket.EndSend to complete an asynchronous send, I occasionally get NullReferenceExceptions and ArgumentExceptions. I can't quite figure out what's causing them, except it looks like it started when I grabbed the new version of the security library-- I think you may have introduced a race by releasing the lock where you did.

Hmm, that's a problem indeed. Could you post a stack trace of the exception you're getting?
Also, is it possible to post example code that hows the problem [a high-level like in one of your previous posts is fine]? I've tried the example projects with the new version of the library, but all of them work perfectly, so I can't reproduce the error.

John, I've uploaded a new version of the library [1.0.13.670] that fixes some problems with the SSL/TLS implementation. I think it will fix the problems you're having.
Can you try the new version and see if it works?