Suppose that you go to your SharePoint site and you no longer see the link to Upload documents to a document library. What the hell? You think. Next you open the ribbon bar, as shown above, and you see that a lot of the buttons are greyed out. All this prevents users from entering information into your site. How can you fix this?
Chances are the site has become ‘locked’. To unlock it, open SharePoint Central Administration and select Application Management from the menu on the left hand side.
Next select Configure quotas and locks from the Site Collection section.
As you will probably see in the Site Lock Information section, the site is set to Read-Only. Change this to Not locked and you site should once again be free for editing and uploading.
Why does it happen? It typically happens after a SharePoint backup failure. Processes like stsadm –o backup lock the site prior to a backup. If that backup fails to complete for some reason the site remains locked and thus read only for users.