st: inicial values not feasible

["Avcharian, Alexis" <avcharian@ort.edu.uy>]

I estimated a biprobit model and stata said:

  inicial values not feasible

I tried different estimations and realized that the "inicial values not 
feasible" problem only occured when i include variable x in the estimation.
i.e.:
biprobit (a = b c d)(t = x y z)     inicial values not feasible

If I don't include x, stata does the regression.
It even works when I include x in the first equation (a= b c d x)(t= y z)
Since x is a very important variable I have to include it in (t= x y z), 
so dropping it is not an option.
Can anyone please give me some advice.
Thanks in advance.
Alexis






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