The "invalid data" error indicates that one of the programming functions used within the application that generated the error has received input in a format that is not matching the one expected (malformed, out of bound, and so on). In most cases, this is a software bug and besides updating the application with the latest service packs or hotfixes there is hardly anything an administrator can do. A reboot/restart of that particular system may clear a particular instance of the problem.
The Task Scheduler in Microsoft Windows may display this error when an account that is no longer available was used to create the task.
In some cases, this error is generated by applications that receive data larger than what the application is expecting (see the link to OA01791). Besides this link there are other posts on the newsgroup related to this error being generated when one attempts to import an SSL certificate into an older version of IIS.
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