use of sub_row_grid not working

I have 2 different grids on 2 diferent pages. Use of sub grid works on one but not on the other. I should be able to figure out the difference, but have been unable to do so. However, I do have the clues narrowed down to this: There are 3 uses of blanc.gif in the file dhtmlxgrid_excell_sub_row.js. By changing each of them to a different colored gif, I have narrowed down that it is only the 3rd instance of the blanc.gif that appears on my main grid. This should help me to figure out where my problem is? Can you point me in the right direction?

sub_row_grid now works in my application. In my main grid, the values in the column where I have placed a setColTypes of sub_row_grid are all empty. However, the excell is expecting the url for the xml file in this column. My column is empty because I intend to form the subgrid on the fly instead of pulling from an xml file. Once I added some neutral value to the column, the excell now functions. Thanks.