我想用STATA 9SE做TOBIT的PANEL,程序不能正常运行，显示如下，求高人指点！！！！

样本是STATA网上的，可由FILE/EXAMPLS DATASETS/ Stata 9 manual datasets/ Longitudinal/Panel Data Reference Manual [XT]/ xttobit nlswork.dta use | describe

. xtintreg inv val cap

Obtaining starting values for full model:
Iteration 0: log likelihood = -597.86009
Iteration 1: log likelihood = -581.03313
Iteration 2: log likelihood = -572.28799
Iteration 3: log likelihood = -572.15911
Iteration 4: log likelihood = -572.15802
unrecognized command: _GetQuad
r(199);