chisq.test error: x and y must have at least 2 levels

Hi,

I use a little script? to make a chi-square-test on 162 factors (it
makes no difference if I take the numeric variant of the factors). At
factor nr. 4 is stops with an error:

[1] "v1= V7.KARTM v11= V7.KAR1M"
Error in chisq.test(d1, d2) : x and y must have at least 2 levels

But x and y /have/ two levels ("nein", "ja"):

 > fbhint.spss1$V7.KARTM

  [1] nein nein nein nein nein nein nein nein nein nein nein nein nein
nein nein
[16] nein nein nein nein nein nein nein nein nein nein nein nein nein
nein nein
[31] nein nein nein nein nein nein nein nein nein nein nein nein nein
nein nein
[46] nein nein nein nein
Levels: nein ja

 > fbhint.spss1$V7.KAR1M

  [1] nein nein nein nein nein nein nein nein nein nein nein nein nein
nein nein
[16] nein <NA> nein nein nein nein nein nein nein nein nein nein <NA>
nein <NA>
[31] nein nein nein nein nein nein nein nein nein nein nein nein <NA>
<NA> nein
[46] <NA> nein nein <NA>
Levels: nein ja

Or is there another meaning of 'levels' that doesn't correspond to the
one returned above?
    Any hints what's going wrong/which mistake(s) I make?