Unable to save my personal models because of an unfamiliar error

Hi experts,
I need a help. I am unable to save my personal models because of an unfamiliar error saying "an unknown error occurred while accessing an unnamed file". Here is a screenshot of the error.

However with this error, it still goes okay along with all functions alright, but the problem is that I can’t save new models.
So, I can say it’s almost worthless to me.
Looking for a help.
Thanks.
