Geant 4.9.5.p01
Ubuntu 11.10

To replicate run:

$dash /path/to/geant4/bin/geant4.sh

which should return the following error

/path/to/geant4/bin/geant4.sh: 30: Bad substitution

The root problem is the check to see if you are running bash or not (line 20):

if [ "x${BASH_ARGV[0]}" = "x" ]; then

Since array variables are not POSIX complaint the check to see if we are in bash will cause non-bash shells (specifically dash) to fail. The fix is simple replace the above line with:

if [ -z "$BASH_VERSION" ]; then

This is a much better way to see if we are running bash. The cmake file that needs patching is Geant4ToolchainBackwardCompatibility.cmake line 84. 

This is a concern because all Ubuntu systems (since version 6) use dash instead of bash during boot and login. So if you put the following line in your '.profile' file

. /path/to/geant4/bin/geant4.sh > /dev/null

In order to setup the environment variables for Geant4 as the installation guide recommends, the script will crash and you cannot login.