FVS336v3 will not upgrade from 4.3.3-5 to 4.3.5-3

Hello,

I'm hoping someone smarter than I am can help with an issue uprgading this firewall. 

Regardless of attempts (all direct hardwired into the router - e.g. not via Wireless) I simply can not get this firmware update to take. The router will accept the file via the admin page, do a quick reboot, then just resume on the previous firmware. I've attempted a hard reboot via power and a reset as well.  Do I have to proceed through intermediate version(s) or something like that, not indicated by the release notes?

Any thoughts or suggestions are welcome.