Mac Mail on OSX 10.8.2 not displaying messages

Since upgrading to OS X 10.8.2 I'm having a lot of problems with my email (works fine on other devices I have). The main one is that isn't not displaying messages, it shows there's 3 new mail messages, but the message list and preview window are empty. This doesn't happen all the time but when it does nothing I do fixes it. Then after a while it will fix itself, then the issue recurs again.

Does anyone know how to resolve this??

Thanks