So install v1.2.0 fails if you have an older version installed on your computer.
To solve this problem you have to remove your old version and install the new after.
However it looks like that removing adobe air applications is a bit difficult for some people so i'll post a little how-to (or go to Adobe Air Knowledgbase with same informations)
Removing Adobe Air Applications for All Systems with the *.air file
- Open the JSONpad air file with your actual version at Google Code JSONpad Downloads. You can get your actual version number in JSONpad > Menu > About.
- Open the air file.
- Remove the application.
Removing Adobe Air Applications for Windows Users
- Select Start > Settings > Control Panel.
- Open the Add or Remove Programs panel.
- Search for "JSONpad" in the programs panel.
- Click the Change/Remove button.
- Follow the steps to remove the application
Removing Adobe Air Applications for Linux Users
On Linux you have two possibilities
1. With a package manager, cause the applications will be installed as native packages (e.g. Synaptic on Ubuntu)
- Just open the package manager and search for "jsonpad"
- Mark the package for removing and apply it
- Go to the directory where you installed JSONpad (normally in /opt)
- Just type "sudo rm -R
Removing Adobe Air Applications for Mac Users
- Go to your applications directory
- Drag and drop "JSONpad" into the trash
- For being sure that it is totally removed clear the trash