Whenever you doing any type of firmware upgrades that involves connecting to a PC or Mac, always connect the USB and make sure the operating system correctly installs the device first before attempting to put the device into any type of update mode. And always disable power modes, screen savers, anti-virus, anti-malware and some times even disabling the firewall completely is a good option. Just remember to turn it all back on once completed. I just did my P1 and yes OSX 10.9 did not allow an update, in all fairness Casio makes no mention of 10.9 support yet but Windows 7 Pro, worked without a hitch.
