I did a screen grab to the clipboard but couldn't paste it into Inkscape -- but I could paste it into Illustrator 8, IrfanView and Fireworks. Why wouldn't it paste into Inkscape?

Thanks.

I don't think that you can do that yet in Inkscape. What you need to do is save your screen shot in another program (ms paint, the GIMP, etc) and then file->import the image in Inkscape.