@willS
Was it working OK prior to this morning? If so, can you think of anything that changed on your system between it last working and just now (any AIR or operating system or anti-virus program updates)?
First of all, please ensure that you are using AIR v33.1.1.744 (links in the post above).
If you are using v50.2.1.1 (or any version after v33.1.1.744), then please uninstall your current version first before installing v33.1.1.744.
Also, try temporarily disabling any third party anti-virus or security software that you might have installed in case this is somehow interfering with JuiceboxBuilder's functionality.
(Please do so at your own risk and be sure to disconnect from the internet first.)
And when i try to make a second gallery the program writes over the first gallery
Until you get things working again, it would be wise to save each new gallery to a separate folder (with a unique name). Create a new empty folder for a gallery first (before opening JuiceboxBuilder-Pro) and then point towards it on the 'Publish' tab (assuming you can get that far into the process).