If I edit a CS File in a .zip and try to save it, it doesn't work. I believe this is your problem too. Here are instructions:
*1. Right click the Blockland shortcut on your Desktop and select Properties
*2. Click Open File Location
3. Double click Add-ons
4. Drag an add-on to your Desktop
5. Move all the contents in the folder to the Desktop
6. Edit what you need to, and put it back in the .zip folder
7. Put the .zip folder back in the Add-ons folder
*if you do not have a shortcut on your Desktop, then replace one and two with these:
1. Go to the Start Button
2. Click My Computer
3. Double click Local Disk (C:)
4. Double click Blockland