406 can be so many things. It is hard to track down from here.
Yesterday I cleared up one that had frustrated me for 6 weeks. It turned out the server has had many hacking attacks and in order to protect the server from these attacks, they loaded some band words.
perl is one of the words. I tried installing a program with a modual that has a call for hyperlink.php. One of the 257 files in the program was named hyperlink.php. Guess what, perl is in the file name = hyperlink
I changed the name to link.php and all the calls and everything worked.
Tracking down this issue may take awhile (if I find it at all.)