I know the discussion took place while ago, but somebody might find this useful.
By now I've used CI session without storing its data in database. Today I decided to give it a try and immediately run across the same problem: CI was generating new session in every page load.
I checked my server time, timezone, my cookie etc. - everything I could find as a tip on forums - with no result. Then decided to debug the CI Session class myself.
Long story short, it turned out that my user_agent field in my session table was too small - VARCHAR 50 - which cuts the original user_agent string - hence CI doesn't find my session and generates onother one. I just increased the user_agent field size to 200 and everything works like a charm.
I forgot to mention that I use Mac OS X Lion.
Again, hope this will help somebody.
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