Since the site came back from maintenance, I have not been able to accept trades.
When I click accept I get the following message - "Error: Failed giving credits."
We're on the same boat. I wonder if there's anything we should update?
I'm using Firefox :(

Same. I'm using Google Chrome at its latest version.
This is what it looks like: https://www.dropbox.com/s/8lqtmafrmfcxb60/Screenshot%202016-12-02%2015.51.58.png?dl=0