This is from the Google help page for Picasa:
"The Drop Box is an online album that serves as a holding pen for several types of quick photo uploads. The Drop Box won't be visible in Picasa Web Albums until you've actually uploaded a photo into it. Once you've uploaded photos to your Drop Box, you can easily move these Drop Box photos to other online albums. Photos can be added to the Drop Box from Picasa, orkut or your mobile phone:"
This is not referring to the app called dropbox, but the drop box folder in Picasa. I am very confident this is what the OP is writing about.
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