Why is Velocity macro not parsing a normal reference notation?

Why is Velocity macro not parsing a normal reference notation?

I have a macro which is parsing on one development machine and not on the
other. I cannot find any differences and wish to know if this is an issue
with the velocity version (currently running 1.6.4) or perhaps something
else.
In my macros I have;
#macro(mylinkmacro $formName)
<a href="javascript: document.$formName.submit();">label</a>
One output is;
<a href="javascript: document.$formName.submit();">label</a>
the other is (where I've given a formName of "myform");
<a href="javascript: document.myform.submit();">label</a>
Where I get the $formName in the output I using running Tomcat 6.0.35.0,
Java 1.6.0_26, Velocity 1.6.4 JAR, Velocity Tools 2.0 JAR and Velocity
Tools Generic 1.1 JAR. I've tried compiling and running this on both
Ubuntu and Win7.
Where I get the myform in the output is a different Win7 and Ubuntu
environment with the same source code.