A weird problem

[Case]

Is there a maximum number of units that you can have advailable for construction in a senario?
I ask this because I am building a senario, and kept adding new unit to the point that about 2/3 of the units were capable of being build by one or more of the active civ's (eg the civ's had the technology to build them) However, the some of the units don't appear on the build list in the city screen. Through experimenting I have found that for each exrta unit I add a unit is subtracted from the build list. And to add insult to injury it seems like I can't reverse this by simply making the unit unadvailable! Is there anything I can do to fix this, or will I have to start all over again?

Thanks in advance
Case

[Mercator]

This has most likely to do with the obsolensence of units:
When the AI can build two attack units, say one with an attack of 3 and one with an attack of 2 (while the other values are the same), the first will only appear in the city build lists of the AI.
Leon Marrick's "Advanced Scenario Design" has detailed information about this. I think it can be downloaded right here at Apolyton, otherwise at http://civ2.sidgames.com

[Alinestra Covelia]

Perhaps slightly off topic here, but relevant:

How many actual units can be on screen at any one given time? The computer has on occasion told me that I have too many...I am wondering whether or not I need to regulate my assignation of units in the scenario to prevent this from happening.

[Mercator]

There's a maximum of 2048 units.