The AI war bit has the advantage of being able to explain the discrepancy in technology between faster than light ships and the DCPU, which seems to be the main thing we need to handle. That said, it's not particularly original. I've been toying with the idea of, rather than there actually being a war between humans and machines, humans just thought there might be, and took preventive measures. Take this for instance:
With the development of faster than light travel, humanity began flooding to the stars. Whether because of disagreement with the recently created global government or simply out of a desire to start a new life across the galaxy, people from all over Earth left their homes and sailed up into the sky. This went well enough for a few Earth decades, until the cultures of the various colonized worlds began inevitably to diverge.
Over the years, improved transportation and communication infrastructure on Earth had resulted in a relatively homogenous Terran culture. However, with light years now separating even the closest of worlds, and communication limited to FTL courier ship which was quite expensive and, while fast, was still far from instantaneous, this unified culture began to divide with each world developing its own local flavor. The Earth government which had been ruling, fairly benevolently, over the colonization process saw this as a threat to its power and decided something needed to be done. The obvious answer was to create some sort of enemy: something that would pose a threat to the colonies and force them to look back to Earth for protection.
Now, while humanity has always been a prolific innovator, there has also always been a certain skepticism about technology as well. Dating back to the 19th century or earlier, there have been concerns that rapidly advancing technology will ruin our way of life. This fear took on a more definite form with the advancement of computer technology and with it, artificial intelligence. Started by old 20th century science fiction and fueled by the incredible advances in technology, this fear was a definite force in everyday life by the time of interstellar colonization. When an automated defense satellite vaporized a civilian shuttle due to a malfunction in the shuttle's transponder, killing everyone on board, the Earth government took it as an opportunity and began warning that the robot uprising had come. They dispatched human soldiers (a rarity by this point) to the colonies to oversee the destruction of any advanced computational technology (and to ensure that the local government remained loyal). This went on without a hitch for a year or two, until nearly all modern computers and means for their manufacture were wiped out. The FTL ships kept flying though, ensuring Earth authority, by use of the massively outdated DCPU.
At this point though, some of the colonial governments took the technophobia even further. The colonies were never the most educated of places and they didn't see the distinction between computers and other recent technological advances, such as the FTL drive. The local governments took advantage of this and began sabotaging the FTL courier system at any chance they got. Earth, unable to remedy this, grew increasingly isolated as one by one, it lost contact with its colonies. After a year of this, Earth, having used up most of its natural resources and having thus become materially dependent on its colonies, began having severe shortages of everything from aluminum to food. With just the support of the few worlds that remained loyal, Earth could not reestablish contact with the other colonies and fell into a period of political turmoil and unrest, with the global government struggling to hold things together.
And here's where the player comes in. This should provide for the varying levels of civilization discussed in the other thread (more technologically backwards colony worlds but also more developed core worlds) as well as explain the technological incongruities. It also sets up a need for trade since people on the colonies still might want technology, so long as it's hidden from the local government (yay smuggling!) while Earth and its allies would need commodities.
Anyway, those are my thoughts on the issue. Please tell me what you think.