Hi there!
I looked through the file attached.
To be honest with you, no one can be 100% sure what the reason is without seeing the PHP program itself.
On the other hand, I already suspect one of the cells to be corrupted. It seems to be quite a common XLS-PHP error. To make sure I am right and you don't hire me in vain, I'd ask you to load first 500 or 1000 lines only. If everything runs OK and displays well in the PHP programm, then I'll be 99% sure how to sort it out and how to avoid it in the future.
But even if the case of remaining 1% happens - there are several cells that don't seem nice to me either (at least they differ from all the others). Normally most php-scripts don't mind cells like those, but as i said before, I'm not familiar with your particular one, so it might be an exception.
Anyway, if there's a problem then there's a solution and it is to be found :)
Kind regards
Alex