All my sites are going down after the 4.1.2 upgrades, with fatal internal server errors and '[an error occurred while processing this directive]'.
What changed in 4.1.2 that could cause this?
I managed to get some sites back up by removing/fixing dodgy queries, so did something with wpdb change in 4.1.2?
Please, give us more information. Installing plugins one by one is not an option. My sites have heavily customized themes. Going over everything line by line would only create more problems/confusion.