When I import my linework from AutoCad into Civil 3d... the linetypes (dashed, hidden, phantom, etc.) are not carried over into Impression. All the linetype are continous instead. I could see this being an issue with hatching if Impression didn't see the dashed lines as a single "connected" line. Is there any way to get the linetypes imported into Impression?
I use a lot of custom text linetypes. To work around this issue, I export my file to a DWF and then open the DWF in Impression3. It breaks the linetypes into lines/text, but at least my text is still there. See if that will work for you.