DSI XL giving error message when R4 cartridge inserted

HelloI suspect that my DSiXL has had a system update on the DSiXL itself....Can't think of why else the R4 cartridges are coming up with an error has occurred.......Is there a way of undoing this update or else resolving this problemThanks

No way to revert the DSi's firmware. You have to either upgrade the R4 to support DSi firmware v.1.45 from its official website, or if none, then opt to buy newer cart that can.