Thank you for keeping at it.
I just tried the "nephi.wright" solution: Created a new folder, gave everyone read/write access and set that up as java temp folder in the preferences. Didn't make any difference.
Strangely, I can't find any errors in system console after running FlexPMD. Eclipse creates a few, but none from PMD.
And even stranger, the "find suspect cut & paste" part of PMD runs just fine.