I don't have an IsatPhone Pro, however I will say that the links to the firmware e.t.c. look very dodgy.
Go to the Inmarsat website and click on support
The URL I have for the firmware is http://www.inmarsateu.net/IsatPhone_...sion_5_3_0.zip
Note that the domain name is Inmarsat
I have just checked the firmware, it is identical to the 'official' Inmarsat version, but you never know, with that domain name it could have been a forgery. Why do these companies do this ?