st: ivprobit error message version 9.1?

["Ms. Marilyn Ibarra" <ibarra@uga.edu>]

I am specifying the following model in my do file: 

ivprobit rremits male edad edad2 (escoacum = momeduc)

I get the following error after it does iteration 0-4 on the 
fitting exogenous probit model and fitting the full model:

"This is version 9.0 of Stata, it cannot run version 9.1 
programs. A free update to version 9.1 is available: type 
update and follow the instructions. r(9)"

Anyone, know what this error message means?  


Thanks,
Marilyn. 
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