Some Programs Slow To Load - Not Recognise Association To File Extension

Some programs are becoming slow to load or do not recognize their connection to a file extension. Most noticeable are Nitro PDF Professional which doesn't always start when I click on a PDF file, sometimes it does, some times it doesn't. Quicken is often slow to start, some times the window opens then it waits for the display, sometimes the there is a wait until the window even opens. Same for xplorer2 opening and even selecting another folder. Going back to Windows 7 with almost the identical installed programs/utilities (about 40) the "problem" goes away.