Have you transferred the app from another developer account to your one? The previous provisioning ID will obviously be different.
UPDATE - For clarification
I have noticed that this answer is getting a lot of views so I will just edit it to include my further explanation from the comments below.
Basically the previous version of your application will NO longer be able to access keychain in order to save secure strings such as passwords (if it contains this functionality). This is because the distribution/provisioning profile it was signed with contains a different ID than the one you are using in your new distribution/provisioning profile because you have transferred your app from a previous account to your new one.
However any NEW versions of your app which are signed with the latest distribution/provisioning profile WILL be able to access keychain as normal in order to save secure data if they need this functionality because they are signed with a distribution/provisioning profile which contains the latest App ID for that app.
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