to me it sounds like you installed GIMP from another user account than
the one you're working with. The user account you are working with
doesn't seem to have execution privileges for GIMP's plug-ins.
Try to install GIMP as administrator or the user account you use for
your GIMP work.
Of course, use your administrator account only for installing and
not for your daily work and even not to browse the internet.
It might not be related to your current problem, but as a general
security advice make sure to scan your downloaded software for viruses.
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