we are very sorry for the inconvenience!
Is it possible that you are using Norton Security 2015?
Norton has a known bug that causes a blue screen while installing / mounting the Boxcryptor drive.
We are in contact with Norton but they haven't released a fix yet.
You find a workaround at our FAQ Section: https://support.boxcryptor.com/display/BCWINEN/Boxcryptor+for+Windows+-+Manual
"I have Norton Security 2015 installed and have problems with Boxcryptor."
Best regards from Germany,