1) Yes, for example: I used the last installer from UAD > 6.3.1 August 2012.
2) No, this is also not done (I think) because I use a whole list of plug-ins from several companies. And: all plug-ins worked before.
3) Logic Pro was both times the first program I installed. Before I made a fresh install of my computer there were no issues.
4) Yes, I saw the reply. But that thread has Mainstage as subject so I first chose an alternative way. *
5) I made a clean install twice and both times I checked a plug-in one at a time. No plug-in will validate. Unbelievable.
* I wrote a mail to someone who works for the company where I bought my computer. It's a specialist in Apple audio and helped me before with an Apogee Duet 2 problem.
I go for a third clean install in a few days and won't do a software update (of my computer) before I tested Logic Pro first.
Don't know what to do else.
Logic Pro 9.1.8 (32-bit) * iMac OS X Lion 10.7.5 (11G63) * Intel Quad Core i7 - 2.8 GHz * 12 GB 1333 Mhz DDR3 SDRAM * 1TB Serial ATA Harddisk 7200rpm * AMD Radeon HD 6770M 512 MB * Apogee Duet 2 * UAD-2 Satellite Duo Core * KRK Rokit 5