A while ago i complained that my BDP9600 could not see the new firmware (v1.60 back then) on my USB stick.
After playing around, i figured the cause.

Don't use NTFS filesystem to format your USB stick.
Use FAT32 to format your USB stick.

After format my USB stick to FAT32 and copy the firmware to the stick and plug into BDP9600.
New firmware detected and completely successfully.

Philips, please make a note in your upgrade instructions!