Hi Colin, Thank you for posting to the forum.
At the moment there are some restrictions on pasting signs away from KeySIGN, especially using 'paste as a block'. We are working on the issues and hope to have made some improvements for the next release.
In the meantime there are a couple of ways around this.
(1) Open the dwg where you are wanting to paste in KeySIGN. Copy+paste should work OK from one KeySIGN drawing to another KeySIGN drawing. Even if you open a KeyLINES drawing in KeySIGN just to do the paste and then reopen it KeyLINES afterwards, that should work OK.
(2) Use the "Export Sign to acad format" menu item (or type EXPORTFORACAD). This will create a separate dwg (like wblock does) in which all the sign items have been turned into native acad objects. You can then use the standard acad INSERT command to insert this dwg as a block into other drawings. Exporting this way will allow you to insert in plain AutoCAD away from KeySIGN.
Sorry to read about the difficulties you have experienced, and thanks for raising the issue so we can ensure things are better in the next update(s). I also hope the above with assist you until then.
Alan Mason, Product Manager, Keysoft Solutions.