If you got some "verbose" messages like "Error loading /Library/ScriptingAdditions … no suitable image found." when executing osascript when within your bash scripts… here is a solution…
You have this kind of message:
because your ScritpingAdditions folder contains some 32-bits only OSAX when SnowLeopard expects 64-bits one…
Error loading /Library/ScriptingAdditions/SOME_EXTENSION_NAME.osax/Contents/MacOS/SOME_EXTENSION_NAME: dlopen(/Library/ScriptingAdditions/SOME_EXTENSION_NAME.osax/Contents/MacOS/SOME_EXTENSION_NAME, 262): no suitable image found.
arch -i386 osascript -e 'tell application "someAppl" to quit'