Integer variable not an integer?

I have a global variable that I set thusly:

$currentLevelNum = 0;

I would then like to use this variable as follows:

%levelgrp = $levelGroup.getObject( $currentLevelNum );

However, when I do so, it doesn't return anything. In fact, the only was I can return something is if I hardcode the integer offset, like this:

%levelgrp = $levelGroup.getObject( 0 );

I've been looking through the threads (albeit not an exhaustive search yet) but have not been able to find anything on this. Does anyone have something they could point me to?

Thanks