After xxx "OK" on the error popup, Outlook displays the available addins. However, there is no addin for MyPhoneExplorer there, as far as I can see, only my "usual" addins. Si I cannot deactivate from Outlook.
Maybe it happens cause a other Addin disturbs the MPE-Addin. If you want to disable the message you can delete the file C:\Programs\MyPhoneExplorer\MyPhoneExplorer_OutlookAddin.dll . If this also brings no result then i can assist you with correcting the registry so that the plugin gets fiully uninstalled.