The issue (and a workaround) are described here: http://stackoverflow.com/questions/22107742/jquery-validation-date-range-issue/
The main thing is that you can't call .element() from within a function provided to .addMethod(). While this is probably a less-common use case, the date range case in the example given is fairly straightforward.
This issue may not be something worth fixing in the current major release, but might be worth considering for the rewrite.
I'm sorry for the lack of activity on this issue. Instead of leaving it open any longer, I decided to close old issues without trying to address them, to longer give the false impression that it will get addressed eventually, especially after several years with no activity. It doesn't mean I'm abandoning the project, just that I'm unable to work through 200+ open issues with the little time I can afford to spend on this project.
To the reporter (or anyone else interested in this issue): If you're still affected by the same issue, please consider opening a new issue, with a testpage that demonstrates the issue with a current version of the plugin. Even better, make an attempt to fix the issue yourself, and improve the project by sending a pull request. This may seem daunting at first, but you'll likely learn some useful skills that you can apply elsewhere as well. And you can help keep this project alive. We've documented how to do these things, too. A patch is worth a thousand issues!