Some folks are running into a bug with Dapper crashing if they have "Collect Album Art" checked in the Options tab of Settings.
First: Open Applications->Utilities->Terminal and type (Copy and paste):
rm -Rf ~/Library/Containers/com.map-pin.Dapper/Data/Library/Application\ Scripts/
Then run Dapper again. If this fails, try Unchecking the "Collect Album Art" checkbox as this box seems to clear things up for the moment. I am investigating to see if I can narrow down the issue and fix it permanently.