That’s probably what’s doing it. There seems to be rounding issues that are happening with plugins like that, where basically the numbers aren’t getting rounded at all when they should, causing a number like 29.9894943944434 to be sent as the amount to PayPal. PayPal cannot accepts amounts like this.
This is a known issue that we’re working to get resolved ASAP. It’s planned to be included in the 1.1.7 release, which I was hoping to get done within a week or two.
That said, WooThemes just released version 2.3 of WooCommerce, which comes with lots of major changes to the development structure that we’re going to have to adjust for. As such, our other plans will probably be delayed a little bit while we play some catch-up.
We do know about this, though, and we’ll get it fixed as soon as we can, so keep your eye out for updates.
I’m going to mark this as resolved since it’s on our GitHub repo issues list, but just let me know if you have any other questions.