Dynamic Multithreading lock
I'm pretty sure you have the potential for a race condition if one thread releases the lock and removes it, after another thread has got the lock but not yet locked it.

Thread one GetLock(someKey) // Creates lock, returns dynamic key
Thread one Lock(dynamicKey)
Thread one complete processing (exits lock section)
Thread two GetLock(someKey) // returns existing key
Thread one RemoveLock // removes lock from collection (not yet being used)
Thread two Lock(dynamicKey) // Now we've locked an object no longer in collection
Thread two complete processing (exit lock block)
Thread two Remove lock // tries to remove a lock that's not in the collection