If the problem you are having is with svBuilder, then maybe a complete uninstall and fresh install will help.
Please try the following:
(1) Uninstall svBuilder.
Mac: Delete the 'svBuilder' file from the Applications folder and empty your Trash.
Windows: Use the uninstaller in the 'Control Panel -> Programs -> Uninstall a program...' list.
(2) After uninstalling svBuilder, please check that there are no files are left behind by manually deleting the following folders from your hard drive (if they exist):
Mac: /Users/your_username/Library/Application Support/Adobe/AIR/ELS/svBuilder
Windows: C:\Program Files (x86)\svBuilder
Windows: C:\Users\your_username\My Documents\svBuilder
You may need to show hidden files to find some of the above locations in Windows File Explorer.
(3) Next, search your hard drive for the term 'svBuilder' and delete any and all entries found (to be absolutely sure that nothing remains).
(4) Reinstall svBuilder following the instructions here.
Hopefully this will help.
If not, please let me know what program or plugin (and version number) you are using to create your SimpleViewer galleries. (Your original post seems to be missing some text.) Also, please explain in greater detail what you mean when you say that "it suddenly stopped working". Does the application open at all? If the application does open, what functionality works, if any? Are any error messages displayed? If so, what do they say?
SimpleViewer Support Team