Theme causing js error when ajax enabled on forms

I'm getting the following js error on forms that have ajax enabled on them:
Uncaught SyntaxError: Unexpected number

This is on the line that calls the js just after the form.

I've identified that it is an issue with the theme as the forms work fine with default twentyeleven theme activated.

Onto resolving the problem... The issue only occurred recently and there have been no real changes to the theme code. How do I go about debugging a theme? As it's only occurring when ajax is set on the form I presume it's a javascript issue.

Any tips on how I can debug this further will be much appreciated!

Okay, that's what I'm doing as a temporary fix. How will I know when the issue is resolved, is it likely to be an update to the plugin or is there a page I should keep an eye on?

P.S. Very quick response, thanks!