hi Cris,
i've seen this in the past on some systems where you tried to open a repo report in the designer. i couldn't find a way via rights to change this error.
to resolve: if the latest copy that you have is in the repository, the only way i found to resolve it was to export the report, as .rpt, from the cmc or your web portal, and then resave it into the cmc as a new report. the bad part of this is that the cuid of the working report will be different as will the ID, so any report to report hyperlinking would have to be adjusted.
i hope this helps,
jamie