if you lost your original keystore file then you will have a problem updating the app.
I don't know how to solve my issue. We published an android app on the Android market. After fixing a few issue, we are not able to release it as a next version of the app in marketplace because w...
you may upload it with a new bundle id and hope people will find it at the store and update it from there.
unpublish the old app and upload a new with the same name and description + pictures and i guess most users will search for the app name and find the new app.
(this is in case you cannot recover the old keystore file)