NOt possible entry in backend

Dears,
FRom last week it’s imposible entry in our backend admin place for manage our website.
If we try to entry to: http://www.plasticagents.com/admin
You can see strange page with this error message:
bgeteam
Warning: assert(): Assertion failed in /home1/marcbg7/public_html/wp-admin/includes/theme.php on line 1

We just update template, and we’re continue having same error.

Our server inform me that they can’t nothing because is related to our current template (Innovado).
Can you help us?

Thank you in

Ticket