How to get rid of "The form cannot be displayed because session state is not available"

I know other people wrote about this in the newsgroups, but strangely enough - no blogger bothered to blog about this - so I will.

When you click on "start workflow" in a publishing site page, you get the annoying error "The form cannot be displayed because session state is not available". This will happen even if the "Configure Session State" in the "Application" section in the administration site is configured properly.
The solution is simple - open the web.config file for the site, search for the word "SessionStateModule" and uncomment that line.

Example:
<!-- <add name="Session" type="System.Web.SessionState.SessionStateModule"/> -->
should be:
<add name="Session" type="System.Web.SessionState.SessionStateModule"/>>