Startup code I've used for the 5282 adds the constant 0x61 to the flash address, not 0x621 as shown in your post. Also, verify that __IFLASH is 0; otherwise you must jump to some non-flash code to actually change the location of flash.
Alessandro wrote:
MOVE.L #(__IFLASH+0x00000621), %D0
MOVEC.L %D0, %RAMBAR0