I suspect someone's probably started playing around with DENY permissions (either for your user/group/role or are trying to lock down the public role incorrectly).

If your user/role definitely has permissions, then I'd look into which other groups you fall into (usually just public unless something like the EVERYONE group has been added) and whether these have any explicit DENY permissions against the schema or the objects.

I'd be pretty sure it's because something has been changed, rather than hitting any kind of bug, so go and bother your DBA's 🙂