Just of curiosity, did this resolve the issue then? I can log on fine with this option 'checked'.
I have people asking about this a lot, and usually advise it's an IT issue at their end, sometimes re-installing the latest application does resolve the issue. But it'd be nice to offer more advice.
Product support has posted this as the solution:
Hi Greg, thankyou for your prompt and precise response. I advised our user to try this, but unfortunately it didn't fix the problem. They are using I.E.9 though, which I suspect may have something to do with it, but I have asked them to contact Autodesk Tech Support directly to resolve the issue.
The error is typically caused by an out of date security certificate, which is unable to update on their machine. If the users PC clock set to the wrong date and/or year can also cause certificate issues, I would check the users time and date settings as well.