The notice list - most of which were my own old 'forum has been updated' announcements - is empty.
Then I try and create a new notice, I get "Please enter a valid value." message. When I try and submit the blank form on its own, I get:
Please correct the following errors:
- Please enter a valid value.
Please enter a valid title.
Please enter a valid message.
...so no hints as to what's blank there.
File Heath Check shows some files in the install directory were "File does not contain expected contents", re-uploading the folder from the full install zip does not fix the messages.