I'm pretty sure dropbox does file versioning, so you should be able to revert to an earlier (uncorrupted) version of your file. Tell me if that works for you, b/c I use dropbox+truecrypt for hosting my super important docs...
When I try to open the file it says The following error occured while opening the database: Hash test failed. The key is wrong or the file is damaged.
I'm not the first one with this problem: http://forums.dropbox.com/topic.php?id=26321#post-163634 and http://superuser.com/questions/187885/keepass-lost-password-...
It does seem like it only keeps 30 days worth of versioning though...
Edit: apparently policy changed at some point and versioning does not count in your quota. Also, Pro accounts need the Pack-Rat extra to enable unlimited versioning.