By any chance are you using the back button?

So what can happen is that you can re-enter the Inbox through an old cached version, meaning it may have an old session preloaded. Usually refreshing the page sorts this out.

You can also replicate a similar effect by editing a post, saving it, and then clicking on the top right hand link to look at the Raw text version. The only way out is through the back button but that will lead back to the old session on your computer of the post. The edits have been saved to the site server but the browser is trying to reduce how much data it downloads by utilizing the temporary internet files.