Nope, not file size, because:

- Easily upgraded to v299 from serial, file size 455k
- Easily upgraded to v271 from serial, file size 505k
- v300 is between those two sizes, at 480k.

Not a problem with the file NAME because it's nearly identical in name to the others that successfully upgraded, except for the 300. And I even tried renaming it to "new.zimage" and upgrading from that. No dice.

Not a problem with the file itself because Jemplode has no trouble upgrading the player successfully with v300 (albeit through FTP not serial).

Is it possible that it's something in the binary data of the file itself... something where a certain sequence of binary characters will screw up the flash pump firmware or the download.c code?

I know that sounds unlikely, but the old Sherlock Holmes mantra is running through my head now: When you have eliminated all other possibilities, whatever remains, however unlikely, must be the truth.

What other possibilities must we eliminate?