R help - Dec 2011 - gmp: Error in solve.bigz(B) : System is singular

With a matrix such as C I do not have any problem:
>library(gmp)
> C
      V1 V2 V3 V4 V5 V6 V7
[1,]  1  0  0  0  1  0  0
[2,]  0  1  0  0  0  1  0
[3,]  0  0  1  0  0  0  1
[4,]  0  0  0  1  0  0  0
[5,]  0  0  0  0  1  0  0
[6,]  0  0  0  0  0  1  0
[7,]  0  0  0  0  0  0  1
> solve.bigz(C)
      [,1] [,2] [,3] [,4] [,5] [,6] [,7]
[1,] "1"  "0"  "0"  "0"  "-1"
"0"  "0"
[2,] "0"  "1"  "0"  "0"  "0" 
"-1" "0"
[3,] "0"  "0"  "1"  "0"  "0" 
"0"  "-1"
[4,] "0"  "0"  "0"  "1"  "0" 
"0"  "0"
[5,] "0"  "0"  "0"  "0"  "1" 
"0"  "0"
[6,] "0"  "0"  "0"  "0"  "0" 
"1"  "0"
[7,] "0"  "0"  "0"  "0"  "0" 
"0"  "1"

But with a matrix such as B I do:
> B
      V1 V2 V3 V4 V5 V9 V13
[1,]  1  1  1  1  0  0   0
[2,]  0  0  0  0  1  0   0
[3,]  0  0  0  0  0  1   0
[4,]  0  0  0  0  0  0   1
[5,]  1  0  0  0  1  1   1
[6,]  0  1  0  0  0  0   0
[7,]  0  0  1  0  0  0   0
> det(B)
[1] 1
> solve(B)
     [,1] [,2] [,3] [,4] [,5] [,6] [,7]
V1     0   -1   -1   -1    1    0    0
V2     0    0    0    0    0    1    0
V3     0    0    0    0    0    0    1
V4     1    1    1    1   -1   -1   -1
V5     0    1    0    0    0    0    0
V9     0    0    1    0    0    0    0
V13    0    0    0    1    0    0    0
> solve.bigz(B)
Error in solve.bigz(B) : System is singular

Can someone help me understand what's going on?