Hi,
If you export this prefab in your fresh project does it work then? if it does, then you simply need to delete the playmaker folder, the ngui folder and the "playmaker ngui" folder, and reimport everything clean, its' important to not attempt just importing as it's not clean enough.
The key to fix your project is cleaning it up, so anything from the asset store or the wiki has to be deleted properly ( don't keep folders and files from that) and reimport again.
MAKE A BACK UP FIRST AND TRY ON A COPY FIRST.
Bye,
Jean