Then I can only suggest that you try talking to one of the people that you know connects successfully using mIRC and ask them how they are doing it.
The only reason I can see for the method that I stated to fail, is if the password is being looked for in a specific manner, rather than just the password.
Example: password has to be passed in the format generated using $md5, since that's how the password is stored on the network. If that example (or something similar) is the case, then we'd need to know just how the password is being stored on the network for the purposes of comparison to the supplied password.
