Misc v3 Bugs: Bills: VIEW/SAVE / Invoices SEND/PAID

1. Unable to VIEW or SAVE bills - 500 Server Error
2. SAVE bills - I duplicated a bill and saved it - gave 500 Server Error but bill has been created - Edited OK but SAVE again gave 500 Server Error
3. It no longer seems possible to mark an invoice as PAID once it has been sent
4. When editing an invoice, the "SEND TO" button doesn't do anything
5. I've just sent (manually) 30 invoices which were ALL copied to me but I did not request copies

Any insights on this? I have the same problem after upgrading to v3. Everything else works fine but when I try and view either invoices or bills I have an error 500