Issue using SGDMA to frame buffer

Do you mean the SGDMA on the Quartus II DVD or the Modular SGDMA I pointed you to? If you are talking about the one on the DVD remember to update the end of the descriptor chain appropriately otherwise you may run into a race condition if the SGDMA catches up with the descriptor you are modifying. By appropriately I mean make sure you update the owned_by_hardware bit in the correct order (always make sure your list is terminated with a descriptor with the owned_by_hardware bit low).