Short description of error
When importing surfaces with pure white, they won't import at all. If they are blocks and imported as dupliface, they will be rotated 90° for some reason and create geometry that is not in the original DXF and should not be there (Despite the dupliface geometry which of course has to be created)
Exact steps for others to reproduce the error
Import this DXF:
One rectangle is missing at the bottom right (only difference with the other rectangles is that its color is pure white. But it is filled and should be displayed.
If you import with this options:
You will get wrong rotation of 90° of the blocks:
If you import as linked instances, the rotation is correct and no random geometry is created.