This Microsoft article Q318378 RepairIE6 seems to have some of the answers you need.

Open IE and click Help, About Internet Explorer and look at the Cipher Strength. It should be 128 bit. If the Cipher Strength is anything less then 128-bit, download and install the Internet Explorer High Encryption Pack.

You didn't mention if you had done this, so I threw this in as well got it from DUX