If you goto your Control Panel for Windows and click the mail icon, then Show Profiles you can add a new profile there and then delete the old, DM should automatically notice this change but if it doesn't goto options and profile settings in Desktop Manager to select the new profile;
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BlackBerry 7100t on Legacy AT&T Wireless
The open dbx and outlook express help has prompted you a path of the Outlook Express files' storage. And now save the damaged dbx files in the safe folder, they can be useful.
In my case, I encountered this same problem when syncing with Exchange public folders (via USB). When I removed the public folders from the sync setup, the synchronization proceeded without a problem.
To continue syncing with the Exchange Public Folders, turn OFF Cached Exchange Mode. One can still use the Cached Exchange mode in Outlook by letting Intellisync sync with an Outlook profile that does not use Cached Exchange mode, while letting Outlook default to a second profile that uses Cached Exchange mode.