I apologize for my incorrect assumption that mircryption has been discontinued. It is only that there have not been any updates on the main webpage for years, there have been no new versions released for years, and the forum posts are not very recent either - plus the helpfile for mircryption states that it has only been tested with even older versions of mIRC, nothing recent.
I will give mircryption and mIRC 7.1 a try and report back with results - problem is that I do not know what the expected behavior is with version 6.14, 6.35, and 7.1 so I cannot spot whether there is a new problem...