Psioncis Unleashed changed name many months ago 9+. Then just recently I re-did the community stuff in to Packs. There is a sticky thread at top of forum. Plus all this information went out in LW newsletter a few weeks ago.
It sounds like you where REALLY out of date. So yes the best method is to do a fresh install as outlined in
FAQ#6.
I am sorry for the issues but this was a MUCH needed and required change to support us all going forward. You can read about that in
THIS post.
In the sticky thread at top any of the update messages like
THIS mention its best to do a clean install. The installer is not handling the massive rename in files correctly on everyone computer. So for some either you have to install multiple times or remove all the addons and install fresh.