We had an upgrade to .Net4 framework on our agenda and did that without any problems, as what we could see. Suddenly we got an issue from an editor that our XForm forms had stopped working. We did the upgrade to .Net 4 with the Nuget-package that exists so that part should be ok, but still we wonder if there's something we missed out in the configuration files or something like that.
All you get after pushing the submit button in the XForm is a reload of the page. We only save the data in the database so there is no problem with any mailserver. Also what I can see it seems like the submit doesn't work as expected, since none of the breakpoints I've had in our added handlers haven't been reached.
One thing that's good in all of this that the error is everywhere, even on our dev machines.
This forum post did solve my problem... http://world.episerver.com/Modules/Forum/Pages/thread.aspx?id=59887
Funny thing though that I had to google it to get to it when it didn't show up in a search here...