The primary reason for this is the loss of connection to your session on the server. This can be a relatively common occurrence when using a WiFi connection; a loss of connection for a second or two can go almost unnoticed, because the WiFi often reconnects immediately. Another common cause for a session termination is unplugging from a hardwired connection and moving to WiFi, for example, when moving with your laptop from your office to a conference room. If your OME session was open during these events, the connection to the server was likely dropped. Even though your browser window still shows you in the OME where you were last working, you are no longer in a live session; OME no longer knows who you are, or what record you are now trying to work on or save. You will need to close your session and log back in to the OME to continue working on this record.
The OME performs an automatic Quick Save on open records every 10 minutes, in addition to any manual Quick Save actions you perform yourself. If your session is terminated due to a loss of connection to the server, you may lose metadata entered since the last system or manual Quick Save.
Aside from loss of connection to the OME server, an additional known cause is browser incompatibility. A primary reason we discourage the use of Internet Explorer for the OME is that IE's code libraries are outdated, as the browser is no longer being updated by Microsoft. As a result, a number of functions requiring button clicks or selections no longer work in the OME; you may be able to log in and do some work, but not successfully Save any of it. For this reason, Internet Explorer should not be used when accessing the OME. We strongly recommend that users work in Chrome when doing work in the OME.