Whenever I try and passthru a command to the server that contains a single quote/apostraphe, it gives me this error:

irc.whatevernetwork.com String Before Apostraphe - Unknown Network

So if I tried to do this: /cs register #chan pass What'd you think is in here
I'd get the error: irc.whatevernetwork.com What - Unknown Network

Any way to circumvent this error (ie. escaping the single quote)?

Are you sure you don't have any scripts loaded? Because it sounds rather odd that mIRC would parse commands that way.

Yes, it does it on a fresh mIRC 6.17 install.

I don't get this problem at my mIRC at all on any network I'm on that has chanserv... so I really doubt it's an mIRC bug.

might just be something wrong with the server or a script you didn't know it was loaded.