The other day, I fried my Bus Blaster. The 20-pin cable I bought did not have polarizing keys. I noticed this before I started using the device and figured I'd always be careful about which direction I plugged in the cable. Bad assumption!
That fateful day I plugged the cable in backwards. I noticed that the CPLD was getting hot (and perhaps the FTDI chip too). I quickly unplugged the cable, but unfortunately the Bus Blaster was toast! I quickly ordered another JTAG pod to keep my work going until I could fix the BB.
I desoldered the CPLD from the BB using my trusty SparkFun Heaterizer XL-3000 (http://http://www.sparkfun.com/products/10326). When I plugged the BB into my computer, I was able to connect to the FT2232! So the FTDI chip seems fine.
Today I received a replacement CPLD (and a new 20-pin cable WITH a polarizing key) from Digi-Key. I soldered the new CPLD on my BB, compiled urJTAG from source, and loaded the JTAGKey buffer configuration into the CPLD. I tested my new (if slightly toasted) Bus Blaster on an ARM development board, and I was able to halt and reset the processor! Success!
Moral of the story: ALWAYS use cables with polarizing keys. I bought the H3DDH-2006G-ND (http://http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=H3DDH-2006G-ND), which includes both a polarizing key and strain relief. (Digi-Key shows this and similar cables as "Value Added Items," which means that they prepare these cables on-demand when ordered. Mine shipped the same day with the rest of my order.)
tl;dr
Use cables with polarizing keys. Cables without polarizing keys destroy your devices, time, and satisfaction.
Thanks for the great summary. I'm glad you got it going again.
You're welcome, and me too! :-)