I have few questions regarding this issue before we start into debugging this issue.
Can you please report where the Program counter is at when the boot fails with the larger image? Have you checked to see if the image from the first page was loaded correctly into memory. Is the NAND FLash part that you are using ONFI compatible? Are you passing NAND parameters from I2C EEPROM or expecting ROM to detect the parameters from the ONFI parameter table.
The boot parameter table for C665x device is loaded at location 0x008fff00. Can you map that to the NAND parameter table structure in tiboot.h file and tell us if the correct NAND geometry is being detected.
Regards,
Rahul