[Tim Wood]

Originally Posted by Craig

However, both of them fail for me when run from a "Run AppleScript" step in an Automator workflow. ("OmniFocus got an error: Some parameter wasn't understood.")

This works fine for me under Automator on both 10.4 and 10.5. Could you try running OmniFocus from Terminal with something like this (assuming you are using bash or zsh):

AEDebugReceives=1 /path/to/OmniFocus.app/Contents/MacOS/OmniFocus

and then invoke your (minimal) script. This will spew a ton of output, so just do the 'activate' bit :)