Strange Drop Box permission issue

I install applications in the Admin Account. I use it for nothing else. If I download an application from a source other than the Mac App Store (such as MacUpdate) I drop the file into the Public>Drop Box of the Admin account, Lately I cannot open thse files while in the Admin Account. It says that I don't have the proper permissions. The permissions on the file seem to carry over and not be over written by the Drop Box. I have made sure that in the folder Info I (System Admin) have read/write permissions, all others write only (Drop Box) How can i fix what is going on so that I can open files in the Admin Drop Box without having to Get Info and apply permissions to inclosed files?