You list 2 issues: 1) appcenter connection error and 2) Over quota issue.
Let’s start with the #2 (Over Quota).
If #1 you can not connect to App Center then how are you testing a mobione app on your device to get an Over Quota msg? My first thought is that you are not using App Center in anyway ‘Over Quota’ error is related to your carrier and data plan or some type of limited resource such as email, hosting provider, ….
Now to #1 are you behind a proxy server that could be preventing MobiOne from connecting to the App Center’s cloud services? Octavio (my support colleague) will follow up with you shortly to discuss this matter further.