Sharepoint "Additions to this Web site have been blocked."

I was at work the other day when i recieved a call from one of my colleagues, they informed me that they could no longer make changes to a sharepoint site, all staff had access to edit and post new items.
I loaded up the site and the first thing i loaded up was the permissions options for the site, straigh away i noticed there was something wrong as my login was the sharepoint farm admin and all i could see was the image below

I initailly thought that someone had changed ther permissions for everyone, i went to the public document library to try and upload a file and i saw the image below.

I did a quick google search but that came up with millions of pages none of them linking me to what i was looking for, i soon relaised what it was, i noticed on the server that for some reason my backups for the sites were still running, they should have finished over night which led me to believe that they had stopped working for some reason, as soon as i saw this i knew what the problem was, the site had become locked for editing.

I connected to the Sharepoint server via RDP and opened up Central Administration, from there i went into Application Management then to Site Collection Quotas and Locks, i selected the Site Collection at the top and changed the option from Read-Only to Not Locked and clicked on OK and the site was working as normal again.

This problem usually appears when the backups are either running or have failed and let the Read-Only flag on the site.