Since upgrading to Yosemite I can get finder to open a folder:
tell application "Finder"
open ("/Users/username/Desktop/testfolder" as POSIX file)
end tell
I cant find info how to make this simple thing work again. Thanks for your help
I am away from my Yosemite Mac at the Mo.
But try:
tell application "Finder"
open ((POSIX file "/Users/username/Desktop/testfolder") as alias)
end tell