jQuery Grid Plugin - jqGrid

When I add option gridview:true to a grid I get the following error:

ts.rows[0] is undefined

addJSONData()jquery.jqGrid.js (line 661)
complete()jquery.jqGrid.js (line 776)
complete()jquery-1.3.2.js (line 3655)
onreadystatechange()jquery-1.3.2.js (line 3607)

if(ir>0) {ts.grid.cols = ts.rows[0]…f(ts.p.records===0)ts.p.records=len;}

The grid is a plain grid (not treegrid or subgrid), and I am not using the afterInsertRow event handler. If I set gridview to false the grid works fine.

Does anybody know why this happens?

Frode