Response by Brad Dinerman
It appears that your GPOs have become corrupt; they may not be repairable. Or possibly you are logging on using an account that does not have access to modify them, though I suspect this is probably not the case.
Do you have backups for these GPOs? If not, then you may need to bite the bullet and manually recreate them, as you’ve indicated you’ve already started to do. If you do rebuild them, make sure to back them up from within GPMC once you’ve completed them, so that you can restore them in the event that they become corrupt again. (And if they do, then you have larger issues to deal with…)