I came across this issue in a design I did recently in PADS where I had a number of plane shapes on the same layer. If I recall this is how I fixed it:
Select the Plane shape -> Properties -> Options (Flood & Hatch) and change the options to Default instead of a hatch grid.
Hope this helps.
Thanks Barry, that was not my exact problem but it led to me figuring out the solution for the Split/mixed planes plotting not being solid. This is what I had to do in addition to checking the options as Barry described:
1) Set Hatch to zero (0).
2) Set Hatch to Orthogonal.
Just setting Hatch to zero still left voids in the Gerber plots, but once it was set to Orthogonal they are solid as I want them. I left the Keepouts as diagonal, they are just for reference anyway.
Actually, to have the copper pour, whether its using copper pour or split/mixed, be closed rather than open hatched is determined by the combination of the line width of the outline and the hatch grid setting in grids. At a minimum, the grid value must be the same as the line width of the outline or less. If it is greater, you will get the hatched pattern you described.
I forgot to mention in my post that the line width/hatch grid relationship applies whether you use default or the custom setting in options as mentioned in the post by Barry. The default merely refers to the global hatch grid setting, while unchecking the box allows you to set a custom hatch grid for that shape.