Import CAD drawing and convert to individual elements

Hi,

I am trying to open a .dwg file in Viso 2007 then convert it so that I can
edit/delete individual elements of the drawing. I have tried opening the
file and inserting the file, converting just a couple of layers as Visio
shapes and as text/lines and also not converting hatches. The conversion
process occurs but I get an error "The file was opened but some problems
were encountered. Details of the problems were added to the log file."
When I open the log file I see this:

Warning] DataType:
Context: VisioDocumentPagesPage ID='0'
Name='Page-1'PageSheetShapesShape ID='2' Type=...
Description: An attribute in this file contains data that is valid but
inconsistent with the rest of the file. Visio has substituted an appropriate
value.

I can then see the layers I selected, but they are all one picture/shape. I
tried ungrouping but that option is not always available and when it is the
individual lines/shapes are still grouped. Is there a way to do what I am
trying to do in Visio?

Thanks in advance for any help you can give me.