The original question was posted in the SCJD forum here, but I will shortly explain what the problem is.
I've noticed that if I set the column widths using:
initially, the table has the column widths as I wanted. Apparently after the model is changed using
it resets the column widths to initial values (all columns uniformly distributed). It also happens if the columns were changed by the user - after he hits the "search" button (the model is changed) and the column widths are reset to the default.