DWG files

Has anyone tried opening ArcBase created DWG files in ICAD? It seems like ICAD doesn't recognize many entities and doesn't display those at all. Any suggestions?Also, I have noticed DWG drawings with quite a few small blocks and hatching taking an unbearable time to open and edit the drawings in ICAD (the original drawings are created in ACAD). Any suggestions or comments to speed things up?Thank you.