Look at how that error message is being generated in the script.
If you upgraded to 10.04, there may still be some pre 2.30 gnome stuff hanging about.
... is interesting - a patch which added a test for gnome 2.26 to the installer config. A shallow reading appears to show that if you do not have 2.26, the error appears. Check on your full script. You want to find out how have_gnome_26 gets set.
Gnome terminal 2.29.6 comes with Ubuntu 10.04 - what does terminal 2.3 have that 2.29.6 does not?