the solution can be found here:
it looks like a lot but that works.
I have copied it here below anyway:
1. Download the Apples official Java Update containing 1.5 from Apples support pages:http://support.apple.com/downloads/Java_for_Mac_OS_X_10_5_Update_4
2 Download a SW called "Pacifist", and install it: http://www.charlessoft.com/
3. Search for 'Terminal' in Finder, and launch it. Once open, go to folder (copy paste this command): cd /System/Library/Frameworks/JavaVM.framework/Versions There, we have to unlink the references to 1.6 version java with the following 2 commands: sudo unlink 1.5 sudo unlink 1.5.0 (It will prompt for Administrator password on first sudo)
4. Now verify that you do not see the 1.5 or 1.5.0 anymore in the list: ls -l If they're not, close the Terminal. NOTE: You HAVE to do this, since otherwise when you install the 1.5 package in Pacifist, it''ll try to overwrite 1.6....and we do not want to do that
5. Open the Pacifist
6. Click "Open Package" once the timer has stopped, and select the file you downloaded in step 1
(note : you need to put the downloaded java file somewhere else than the download folder. On the desktop worked for me)
7. Browse the folderpath under the path: Contents of the JavaForMacOSX10.5Update4.pkg/System/Library/Frameworks/JavaVM.framework/Versions
8. Select the 1.5.0, right-click on top of it while it's highlighted and select "Install to default location". Repeat for 1.5
(note: you need to drag and drop J2SE5.0 32 bits and J2SE5.0 64 bits above Java SE 6 in the Java Application window. No need to touch the first window that is for browsers.)
9. Close Pacifist.
10. Via Finder, go to "Application -> Utilities -> Java Preferences", and drag & drop the 1.5.0 in list above 1.5.0.
11. Done, launch the Line6 Edit!