Logging in after hours on iMac results in blank screen and forced reboot

I have an iMac where I run Online Family Safety, and there is an issue which is causing grief several times a week.  The issue is the following:

 

I have Norton Online Family set up to not allow logins after 11:00 PM or before 6:00 AM - but occasionally I need to log in during the blackout times.  When I do so - I am able to log in to my iMac user - only to be automatically logged out after about 5 seconds with no prompt from Norton Online Family to extend the time.  Once I am automatically logged out, the only thing left on the screen is the background image - no menu bar, no desktop icons, no dock.  At this point the computer never recovers (I have let it sit all night before) and I am forced to hold the power button for 10 seconds to force a reboot.

 

This is not good and I would like to know if there is a fix for this.

 

Thanks in advance

 

I have an iMac where I run Online Family Safety, and there is an issue which is causing grief several times a week.  The issue is the following:

 

I have Norton Online Family set up to not allow logins after 11:00 PM or before 6:00 AM - but occasionally I need to log in during the blackout times.  When I do so - I am able to log in to my iMac user - only to be automatically logged out after about 5 seconds with no prompt from Norton Online Family to extend the time.  Once I am automatically logged out, the only thing left on the screen is the background image - no menu bar, no desktop icons, no dock.  At this point the computer never recovers (I have let it sit all night before) and I am forced to hold the power button for 10 seconds to force a reboot.

 

This is not good and I would like to know if there is a fix for this.

 

Thanks in advance