in reply to loss of dll in a multi threaded app

Your problem description is rather too vague to allow an answer.

What error are you getting that is causing you to believe that you have "lost a dll"? What is the line of code that produces that error?

The best way to get help with your problem, is to reduce it to a minimal testcase and post the code, That way we can try it out and see if the problem can be recreated outside of your environment. We will also be able to see what mistakes you are making (if any).

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
The "good enough" maybe good enough for the now, and perfection maybe unobtainable, but that should not preclude us from striving for perfection, when time, circumstance or desire allow.

In Section Seekers of Perl Wisdom