Saw this on a different site and wanted to share:
Only works for jailbroken users that are on 4.0 or 4.0.1.
1. Get/Purchase iFile (you can use SSH too).
2. Go to /System/Library/CoreServices.
3. Locate the file called "SystemVersion.plist" and just tap it once.
4. Press the "Edit" button in the upper left.
5. If you are on 4.0 edit the "8A293" to "8B117", if you are on 4.0.1 change the "8A306" to "8B117".
6. If you are on 4.0 edit the "4.0" string to "4.1", if you are on 4.0.1 change the "4.0.1" to "4.1".
7. Now press "Done" on the upper right.
8. Reboot (Respring doesn't work), and install the new iMovie from iTunes
http://www.ipodtouchfans.com/forums/showthread.php?t=310552
Only works for jailbroken users that are on 4.0 or 4.0.1.
1. Get/Purchase iFile (you can use SSH too).
2. Go to /System/Library/CoreServices.
3. Locate the file called "SystemVersion.plist" and just tap it once.
4. Press the "Edit" button in the upper left.
5. If you are on 4.0 edit the "8A293" to "8B117", if you are on 4.0.1 change the "8A306" to "8B117".
6. If you are on 4.0 edit the "4.0" string to "4.1", if you are on 4.0.1 change the "4.0.1" to "4.1".
7. Now press "Done" on the upper right.
8. Reboot (Respring doesn't work), and install the new iMovie from iTunes
http://www.ipodtouchfans.com/forums/showthread.php?t=310552