I tried to do reproduce this issue here running Ubuntu Lucid but works fine for me (under similar conditions). This is that I did such as a possible work around:
1) Create a new shorcut with name Capture Area and command /usr/bin/gnome-screenshot --area
2) Then assign a shortcut to execute this function (I assigned Control + Impr just for testing porpuses)
3) Press Control + Impr and voila.
I tried to do reproduce this issue here running Ubuntu Lucid but works fine for me (under similar conditions). This is that I did such as a possible work around:
1) Create a new shorcut with name Capture Area and command /usr/bin/ gnome-screensho t --area
2) Then assign a shortcut to execute this function (I assigned Control + Impr just for testing porpuses)
3) Press Control + Impr and voila.
Regards