Just did a full clean install of P3D5.1.

Have installed FSLabs A320 and 321.

FS2Crew shows this when opening the configurator: "FSX/FSX:SE/P3D path not located properly. Please launch FS2Crew Manager from Main_Simulator_Folder\FS2Crew2010\Versions\Airbuslabs"

Getting frustrated here, I think I've tried everything. The addon.cfg shows the FSLabs btw:

[Package.4]
PATH=C:\FSLabs\FSLabs
TITLE=FSLabs Aircraft Family
ACTIVE=true
REQUIRED=false

When you installed the Labs aircraft, did you use the default install folder or did you try installing things to custom locations?