I am getting the SAME exact problems cited by Remus and Ian.
VERY slow opening of PDF files. Even tiny 24 kb PDFs take almost 30 seconds to launch program and open. Files open faster when Nitro program is already open, but leaving Nitro constantly open is NOT a solution.
As Remus states, "when it opens, I can see, for a few good seconds, only the margins of the program (the toolbars), the middle being occupied by Windows's File Explorer." This has been occurring since I purchased and installed Nitro Pro 13 on Dec. 31. Completely unacceptable.
Now, I am also getting the initial Error message "An error has occurred within our system. Please try again or contact support if this error persists." After clicking "OK" - I get the follow-up Error citing "(Error 401)".
Have also tried to "repair" the Nitro software by uninstalling, rebooting and re-installing. Problem never went away and persists.
I am running brand new Window 10 and Nitro Pro 13.8.2.140.
Need new version and working software ASAP.