100 Units Bug
RA2 and YR (and probably TS and FS as well) are coded in a way that limits the number of total buildable VehicleTypes, InfantryTypes, and probably AircraftTypes as well, to 100 units each. If you have a buildable object on a place after 100, the AI will think that is the only unit buildable and create it over and over again. Literally. It will continue building until there is no money left or you stop it. This bug can partly be avoided, see below for details.
Avoiding the 100 unit bug (by DCoder)
Look at your [InfantryTypes] and [VehicleTypes]. How many entries do they have? If there's more than 100 buildable units (those without TechLevel=-1) and the're not all in the first 100 lines of the list, the AI will go nuts - it'll build the last unit in the list non-stop, and won't attack. To avoid it, you'll need to rearrange these lists, put buildable units first and the civilian and dummy units in the very end. I personally sorted it like this:
[notice the gap here]
Note the allied stuff is first, next soviet and yuri, then there's a gap between 43 and 100 before civilian units are listed. The numbers don't really matter, only the order of the list does. Now I see that I have 43 buildable units, and can still make 57 extra ones without screwing up. Note that HOWI and VLAD are in the buildable units list, because I made them buildable, it's not a mistake :)