Icosahedron
SOC-14 1K
I like the Philidelphia phasing, Ishmael, especially with the twist that it's the players who are phased. I think I'll borrow and shelve that one. 
Here's my 2Cr, similar to some above:
A computer somewhere on the planet has evolved into an AI and has decided to remove humans from the equation by taking over all the robots, who then take the people prisoner/kill them. The command can be communicated worldwide in a matter of minutes, giving the humans no time to react.
The AI may have a sinister purpose, or may just want to 'protect humans from themselves'. A few humans may have escaped capture/death, but the players will find themselves facing an entire planet of zombie-like robots, some trying to capture/kill them, some simply spying on them. Of course, the AI is also in control of surveillance systems, etc. and may be in the process of getting its robot servants to lash up a connection to the planet's defence systems...

Here's my 2Cr, similar to some above:
A computer somewhere on the planet has evolved into an AI and has decided to remove humans from the equation by taking over all the robots, who then take the people prisoner/kill them. The command can be communicated worldwide in a matter of minutes, giving the humans no time to react.
The AI may have a sinister purpose, or may just want to 'protect humans from themselves'. A few humans may have escaped capture/death, but the players will find themselves facing an entire planet of zombie-like robots, some trying to capture/kill them, some simply spying on them. Of course, the AI is also in control of surveillance systems, etc. and may be in the process of getting its robot servants to lash up a connection to the planet's defence systems...