On reopening my AutoCAD 2015 application, all of my toolbars have dissappeared. The basic options (line, circle, etc.) toolbar is missing, layers is gone as is the toolbar that usually displays paper/model space and the snap/constrait options. The File, Edit, View, Help options that are usually displayed beside 'AutoCAD 2015' in the top left corner have also dissappeared.

This has happened several times and each time previously I have resorted to uninstalliing and reinstalling the programme, which is a nuisance and means I loose all my prefence settings and plotstyles etc.. 

Has anyone encountered this problem before or know a possible solution?

I really don't want to have lost all plotstlyes again.

I have updated the application in the past few days so it's at the latest version, but i've had this occur several times so the new version is not the issue.