You can see what item was the cause of declaring the OOS if you use Gerike's OOS Logger (search for posts by him, or snag it from Fall from Heaven or Fall Further. Probably a lot of other mods that have it incorporated as well out there). I've enhanced the version in Fall Further a little bit to have a better naming scheme for the log file (lets you check OOS doing MP on a single computer, and records more city data, stuff that can't be checked for an OOS, but can help you translate the other information).
Also enable random number logging in the ini. Again, the default of this is horrible for trying to check MP on a single computer as it saves everything to one location on your machine. And I am not sure how easily you can compare the default as I didn't know about it until I had already created my own logger for tracking Randoms only. If you are comfortable in the DLL (at least with merging other people's changes) you can check out the source for Fall Further and snag what I did there (it is a single small change in CvGame)
