The token being referred to is your login session token. It's easily renewed by accessing a forum page, that's if your account is set to keep you logged in, or you'll have to log in again.
This has happened to me while composing long posts with lots of content. I have also found that there is also a clock for photo attachments. Uploading images with the paperclip tool works if you immediately put the links into your post and get it submitted, but wait too long and you'll need to upload them a second time.
Attached images - type in place holders, something overt that stands out and will be easy to find. When you are ready to submit your post, go to the paperclip tool, upload your images, and replace you place holders.
Post content -
a: Depending on your browser, you can hit the back page button to take you back to the composition page and hopefully everything would be buffered. If not that means starting over.
b: Type for as long as you want, but pause before you go ahead and click Submit. Move your mouse up to the Blue bar of links and right click on any choice. You'll get a pop up window with an option to "Open in new window". This will open a new window to that page, but in the processed of web site access, it will refresh your token. Now go back to the composition window, and safely click "Submit"
On a side note, did you get my email send to the address from your website ?