Allin and Jack: Thanks for your prompt reply
For accessing the coefficients, using the new naming scheme
($coeff(x1) rather than coeff(x1)) has indeed solved the problem.
you can also do
probit y x
xb = qnorm($yhat)
which is not optimal, but does the job.
I did no know about the qnorm() function. It seems to me that it is
not mentioned in the documentation (User manual & Command Reference).
For sure it is not optimal, but much better than the workaround I had in mind:
probit y 0 x1 x2 X3
genr xb = $coeff(0)
loop foreach i x1 x2 x3
genr xb = xb + $coeff($i)*$i
endloop
Best wishes,
jean