It sounds like the 'New Gallery...' and 'Open Gallery...' buttons are non-responsive.
Is that correct? If so, try closing JuicenboxBuilder-Lite and manually delete the following folder from your hard drive.
Mac: /Users/your_username/Library/Application Support/Adobe/AIR/ELS/JuiceboxBuilder-Lite
Windows: C:\Users\your_username\AppData\Roaming\Adobe\AIR\ELS\JuiceboxBuilder-Lite
Now re-open JuiceboxBuilder-Lite and see if it works OK.
If this does not work, then try completely uninstalling and reinstalling JuiceboxBuilder-Lite following the procedure in this forum post.
(Just replace all instances of 'Juicebox-Pro' with 'Juicebox-Lite'.)
If you continue to experience difficulties, then perhaps you could upload a screenshot somewhere to show me what you are seeing and let me know what button or link you are trying to click (exactly what text is on the button or link) and what happens (or does not happen) when you click it.