How much RAM memory and free hard drive space does your machine have? What happens when you try to open the second document? What method are you using to open the 2nd document
The HP PC is running with 3Gb Ram, enough Free Discspace (over 100Gb Free).
It happens nothing when i try to open a second PDF. I always open the PDF Documents directly with double klick.
But now i got the problem resolved by myself. I deinstalled version X and installed Version 9. Now it works fine again...