Error when trying to post articles

[cb1100r]

I have just created a test site for V5 upgrading from V4 on a copy of my database. When I try to create an article all goes well until I try to POST or save as DRAFT. I get an Error "Invalid Request". Do you think I have an error in the Database somehow coming from the Upgrade.. or is it something more fundemental.. there's no clues I can see as to where to look.

[Wayne Luke]

Would need to know what the invalid request is. Though a database error would usually trigger a different error response.

What does it say in debug mode? https://www.vbulletin.com/go/vb5debug