Displaying a tag cloud from a plugin

Hey all, I’m writing a widget for WordPress that would of course be used as a plugin.

In function(widget), I have some arguments for the tag cloud that will accept what people enter in the widget control panel, and then just have:

wp_tag_cloud($my_args);

This works fine and spits out a snazzy tag cloud in 3.2.1, but on 3.1 and lower I can’t get anything to be output.

Any idea on what’s going on here? Thanks!