[Limdep Nlogit List] nlogit, crosstab, list

[RAUX Charles]

Hello,
I am trying various options of nlogit and getting weird or no results.
I try
nlogit ;choices=air, car, bus, train, none
       ;lhs=choicem
       ;model:U(air, car, bus, train, none)=<asca, ascc, ascb, asct, 0>
             +<da, dc, db, dt, 0>*duration+pc*price
       ;show model
       ;describe
       ;crosstab
       ;keep=pp$

The model estimates fine, the option keep too. But with crosstab I get only zeros in XTAB_PRB and XTAB_FRQ.
When I add "list" the predictions are listed
PREDICTED PROBABILITIES (* marks actual, + marks prediction.)
Indiv    AIR        CAR       BUS       TRAIN     NONE
    1   .4223*+   .3993     .0686     .0593     .0505
    2   .2120     .0752     .0054     .6232*+   .0842
...
But I get an error message "Error    803: Hessian is not positive definite at start values."
And some parameters are fixed. This error doesn't happen when I don't use the option "list".
What is wrong with these two issues?
Charles Raux