I also experienced this as OP described. After playing further, I like Vyarloq decided it wasn't an issue that a load Autosave couldna fix in a jiff.
Spartanleonidus
I find my early research order very similar to Bryce's. I don't go to heavy magic early because my Sov is not high enough level to have a high Int. I prefer getting to at least light plate then look towards Cedar Long Bows (for Sov/Heros) and use built units as blockers/tanks.
Once I realized that there was a limit I used it as a way to help me decide what cities should be focused towards. My front line cities get command posts, archery ranges etc. I put granary, garden and irrigation in every city to allow for a larger civilization. I pretty much put a limited number of workshops, study, and arcane studies once I have a large (>6 cities) and focus on their specialty buildings.
I also see OOM drops at different times. Win7 64, 8GB RAM
I have nearly identical system specs as OP and see the crash what seems like more frequently then that. I may try this is I get to more annoyed. I have 8GB and never see my total system usage go over 4GB (while playing Elemental) so maybe this will allow it to eat/leak RAM till it canna no more? That IS why I bought more RAM than absolutely minimum.