[Help-glpk] a simple question about using glpk

[Wei-Lun Hung]

Hi, there
I am using glpk to solve scheduling problem. I encountered a simple 
problem but couldn't figure out why is that.
The error message I got is 'lpx_load_matrix: ja[55] = 7; column index 
out of range"
Does this mean I cannot have fewer structural variables than variables 
in the raw constrains.
For example, the objective function of my problem is like this:

Min A1I1+ A2I2 + ... A6I6 (there are only six columns)
st.
C11 + C12 + ... + C19 = C1  (I have 9 variables here)
...

How could get around of this problem?
Thanks in advance.

Wei-Lun