When you try to apply Hot package in 3.x and 4.0B you may get error during Test Import Phase because of repaired objects.You have to reset flag by:
1. by SE03-->change object directory
2. select repaired object and display
3. select goto-->changes-->without transport.
4. double click on object and press SHIFT+F7.
5. select goto-->changes-->With transport.
You can continue on application Hot Package.
Also in case you copy all object in a development class from one system to another You may have difficulties when trying to change copied objects. System prompts that you are repairing that objects so you have to take a key for that object. As the original system for that objects still the source system, you have to change original system of copied object.
For that use the following procedure:
1. Execute SE03
2. Choose "Change Object Directory Entries"
3. Select your objects ( TIP: to change all objects belongs to Source System, Write Source System Name in "Original System" box ) and execute.
4. Select Goto-->Changes-->Without transport.
5. Change Original System to Target System.
6. Select Goto-->Changes-->With transport.
Now you can change your object without repair prompt.