If you encounter an error stating that your account does not have permissions to submit bugs when using the Send Feedback feature in Windows 7, there is a straightforward way to resolve this issue. Since you downloaded the beta version from the MSDN site and did not explicitly sign up for anything, you may need to register or find an alternative method to provide feedback. While you mentioned trying the Microsoft Connect site without success, there is another avenue you can explore to submit feedback for Windows 7. You can follow the link provided in the edit of your post:
Give Feedback for Windows 7. This link should direct you to the appropriate place where you can sign up and share your feedback for the Windows 7 beta version...