First off all, congratulations for more one usefull and simple to use component. Really amazing.
I found a little bug on dhtmlxvault 1.6. when you limit the number of files (by exemple, 5), select 5 files to upload and do the upload, the add button remains disabled after the upload completed.
A similar bug occours when you limit files (like 5 by example) and upload 2 files. After that, you can select only 3 files after click on “clean” button.