In one of the updates to the blacklist last night the following appeared.
[%Random line from Custom Field 3%]
This broke my auto generated Htaccess file and gave 500 codes.
All is well now as I removed this entry from my local list.
If others might be encountering problems, this could be it.
Jon
I just found that item on the central blacklist and got rid of it. I don't know what it is or how it got there. It won't go out from now on, but anyone who has it already can delete it from their local blacklist.