[Limdep Nlogit List] calculation of standard errors

[Philomela at gmx.net]

Dear all, 
i am estimating standard errors for willingness to pay estimates using nlogit by inserting the parameters and the covariance matrix which is estimated using some other software. 
Unfortunatly i get sometimes the message that i cannot get standard errors due to fixed parameters:
Is that possible or may it be due to a mistake when transferring the data?

Thank you very much, 
Philio

+-----------------------------------------------+					
| WALD procedure. Estimates and standard errors |					
| for nonlinear functions and joint test of     |					
| nonlinear restrictions.                       |					
| VC matrix for the functions is singular.      |					
| Standard errors are reported, but the         |					
| Wald statistic cannot be computed.            |					
+-----------------------------------------------+					
+---------+--------------+----------------+--------+---------+					
|Variable | Coefficient  | Standard Error |b/St.Er.|P[|Z|>z] |					
+---------+--------------+----------------+--------+---------+					
 Fncn(1)       8.68888889          1.414   					
 Fncn(2)       1.24444444     3.55198724      .350   .7261					
 Fncn(3)      -3.44444444     4.14932377     -.830   .4065					
 Fncn(4)      -57.4444444     28.5562790    -2.012   .0443					
 Fncn(5)       13.9642857     1.12938488    12.365   .0000					
 Fncn(6)       1.42857143     1.12938488     1.265   .2059					
 Fncn(7)      -30.5357143   ......(Fixed Parameter).......					
 Fncn(8)       -.03571429   ......(Fixed Parameter).......					
 Fncn(9)       14.9285714     4.07205509     3.666   .0002					
 Fncn(10)      16.0714286     3.91230398     4.108   .0000					
 Fncn(11)      1.14285714     4.37408883      .261   .7939					
 Fncn(12)     -4.68888889     4.81692897     -.973   .3303					

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