How to open the terminal? (Mis-configured the profile)
Solution 1:
Sounds like you've botched your profile up slightly by adding a custom command (something that runs as soon as it opens).
Thankfully you can edit your profile settings by running this (use Alt+F2):
gconf-editor /apps/gnome-terminal/profiles/Default
If you've botched up too much you can use the Etch-a-Sketch method and reset everything back to defaults:
gconftool --recursive-unset /apps/gnome-terminal/
Solution 2:
The command
gnome-terminal -e bash
will work around the profile command setting.
Once started, you can modify the profile.