I have had fsx+acceleration installed for over a year on my pc.

Recently on long haul flights I get the "your trial period is over please register flight sim now" pop up.

Clicking the message crashes the sim.

Any ideas what is causing this?

Right click on the fsx.exe and select properties.  If compatibility mode is selected under the Compatibility Tab, uncheck it and restart FSX.  If the problem still exists, I think you have a registry problem where it got somehow corrupted.  The only solution I know of (and via Google) is to completely uninstall and reinstall FSX and reactivate.  Not too many people have had this problem.  Before you uninstall/reinstall though, did you check your system for viruses.  Run a system registry cleaner such as CCleaner?

 

Best regards,

Jim