Sprout Forms - An unknown error occurred when trying to view entries in CP
You're experiencing two different things.

First, as Johannes suggested, if you update to the latest version of the plugin (using the same url that you were sent for the private beta), the error in the control panel will be fixed.  This issue was introduced in Craft 2.3 and was resolved in Sprout Forms 0.8.3

Second, it sounds like you have some issues with Email Notifications.  Assuming you have all the Form Notification settings in place and functioning email, as it sounds like you do, we recently discovered a bug where email notifications are not sent if you are using ajax to submit your forms.  We have a fix we can send you, and it should be resolved once we have a chance to release that and a few other fixes in Sprout Forms 0.8.4

Please send us a note if you have any more questions and we'll get you the updated file if you need it before we get those updates into the next release.

Ben