Check for codes in the computer related to anti-theft and try disconnecting your battery for a few minutes and reconnecting it.
I just recently had something similar replacing an alternator on my 03 Cobra and afterword the car would crank over but not start and when I checked the computer there was an anti theft P code (think it was P1624 Anti theft system). Cleared the code, disconnected and reconnected the battery (again

) and everything started right up.
It wouldn't be blocking the starter from spinning though, unless there are variations that I'm not aware of. On my 03 that is an external hard circuit between the ignition switch and the starter that has nothing to do with the anti-theft system. The PATS system just disables the electronic fuel injection and ignition from firing by completely disabling the engine computer.
Totally unrelated and nothing to do with your problem but another thing to keep in mind for future no start troubleshooting that is common is the fuel cutoff switch in the left side of the trunk that can pop. It works similarly to a circuit breaker and needs to be reset if that's the case.