This issue is really only seen in two cases: 

The most common cause, is when a 2nd account session is opened on another device or in another browser for the same account. Only one account session can be open at any one time for each user account, although several browser tabs in the same browser can be open. To resolve, try the following:

When you see the 'Glog could not be saved' message please, initially, try to save again. If it still won't save do this:
  1. Open another tab in the same browser, go to http://edu.glogster.com/login/ and log in to the account again.
  2. Return to the 1st tab (where the glog will not save), the glog will now save correctly.

The 2nd, less common, reason is if the firewall settings at your location are not set correctly. In this case the following link should be passed to your network administrator: