Consider the following string:

MAVEN_OPTS="-Xmx1280m -XX:MaxPermSize=512m" JAVA_HOME="/opt/java/jre/1.5" 

the splitEnvironments() method in the Command Class tries to be smart an not split on space within the quotes. However, it greedily matches for quotes so it will pick up:
"-Xmx1280m -XX:MaxPermSize=512m" JAVA_HOME="/opt/java/jre/1.5"
as the quoted string and not split spaces rather than:
"-Xmx1280m -XX:MaxPermSize=512m"

So the above string wont get split into its two properties, and the build dies...