ivreg2 warning covariance matrix of moment conditions not of full rank

Dear Stata Users,
I was trying to estimate an IV regression (2SLS)

I have few dummies in my model, the dependent is a binary variable of benefit's claim and I am instrumenting the amount. I use weights to correct for sampling issues.
I got this error at the end of my 2nd stage results table

Code:

 ivreg2 nclaim age age2 married ib3.edu i.eu_nat i.pgemplst_gen i.howner i.singlep i.dis_dummy  i.female i.east ib2.citysize i.haskids  (ben_amt=  prvtransfers needs) [pw=hweight] if  head==1, first 
-----------------------------------------------------------------------------------------------------------
Underidentification test (Kleibergen-Paap rk LM statistic):            146.799
                                                   Chi-sq(2) P-val =    0.0000
------------------------------------------------------------------------------
Weak identification test (Cragg-Donald Wald F statistic):             1545.588
                         (Kleibergen-Paap rk Wald F statistic):        165.936
Stock-Yogo weak ID test critical values: 10% maximal IV size             19.93
                                         15% maximal IV size             11.59
                                         20% maximal IV size              8.75
                                         25% maximal IV size              7.25
Source: Stock-Yogo (2005).  Reproduced by permission.
NB: Critical values are for Cragg-Donald F statistic and i.i.d. errors.
------------------------------------------------------------------------------
Warning: estimated covariance matrix of moment conditions not of full rank.
         overidentification statistic not reported, and standard errors and
         model tests should be interpreted with caution.
Possible causes:
         singleton dummy variable (dummy with one 1 and N-1 0s or vice versa)
partial option may address problem.
------------------------------------------------------------------------------
Instrumented:         ben_amt
Included instruments: age age2 married 0.edu1 1.edu2
                      2.edu3 4.edu4 1.howner 1.singlep 1.dis_dummy  
                      1.female 1.east 1.citysize 3.citysize 1.haskids
Excluded instruments: prvtransfers needs
------------------------------------------------------------------------------

I don't know what to do here with this error message. The results show the coefficient of the instrumented variable/ ben_amt -.007962 to be be significant (P-value 0.095 ) though weakly significant. The two instruments used are shown to be strongly significant in the first stage results (both p-value 0.000)