Meantime try going to www.adroidtablets.net anther forum. Also Android.net another one.
Additional meantime.
While unit on remove the sd card then the battery restart it and if it still happens do a system reset.
(from a search of the second forum) from past on PC problems power off for around 3mins. Powering back on seems to kick them back in to working like kicking a temperamental car that won't start.
And don't forget to come back to this site and look for other solutions or to say its now working and what you did for others who have the same problem
Bob UK
May 2015