I too have a DKB3128. I too have double sided 16 chip Kingston KTM7318/64 EDO SIMMS and like you I also only get 64Mbytes of RAM.
(Nice to know someone else has the same problem and my DKB3128 isnt screwed!)
I tried a mix and match of SIMMS to try and get above the 64Mbytes but no luck (BTW: You need the software installed to mix and match SIMMS)
I have an Amiga 4000, buster 11 etc.
I contacted the Creator of the DKB3128 "Dean Brown" and he assured me that everything should work.
I keep meaning to try and get some Fast-Page-Mode (FPM) Simms instead of EDO see if they are any better.
It's definately these SIMMS I fear. I payed £8 each for my SIMMS so I didnt want to replace them straight away.