The most common solution to this is refreshing your browser window while bypassing the cache. Wikipedia has a good writeup on how to do this.

This particular issue can occur for the following reasons:

• The browser timed out before the page was completely finished loading.
• The internet connection from your provider timed out just as the signature was posting.
• Our server was interrupted.

If refreshing the page using the above instructions does not resolve the issue, please submit a request to our Help Desk. Please be sure to include the following:

• Operating system version
• Browser version (how to check)

Here's an example of the information from whatismybrowser.com we need to help diagnose this issue. This is Firefox 10 on Mac OS X 10.7.

Browser version (full) 10.0
Operating system version (full) 10.7
User agent string Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:10.0) Gecko/20100101 Firefox/10.0