Gorbies,
Actually, you need to re-run the main PT10 installer AFTER the Instrument install, as the PT10 installer updates some of the instrument plugins. Then you need to run the wee program in each of the instrument's folders to redirect the location of each library ("Set Content Location").
Sorry this is a bit of a hit and run post, I spent ages tracking down this info myself when I had problems, but can't quite put my hands on it now. Give it a try and I'll keep looking for the bits and pieces I collected (for instance had to do a Google search instead of a search on this forum to find certain tech support pages that describe this).
Cheers
Steve Bush
www.music180.com/pros/5887
MacPro 4.1 (Nehalem) 2.26 8 Core, OSX 10.6.8, PT10HD, 14 Gig RAM, PCIe HD3, 192, Sync I/O, Midi I/O.