Works perfectly, thank you very much.
Édouard
I found the problem. It has to do with the code in the displayline script that Skim uses. The last line in that script should have been:
/usr/bin/osascript -e "tell application "Skim"" -e "activate" -e "open POSIX file "${file}" at TeX line ${line} from source POSIX file "${source}"" -e "end tell"
Note that the ${file}, ${source} etc are not surrounded by quotes any more.