I have Adobe Audition v2.0 (build 5306.2), Ahead Nero - Burning Rom v220.127.116.11 and filter from http://www.saunalahti.fi/cse/files/cool_neromp4.zipEverything works for me including decoding. Check if you made everything correctly. For example putted filter into the same folder as Audition.exe.Also my personal thank to man behind this filter.
Hmmm... What are you doing? If you want to use Nero's encoding routine in Audition then you don't need to install some 7th and some 6th generation at the same time. Also you don't need to put DLLs from Nero into Audition's folder. The filter above just takes the placement of the needed Nero's dlls from registry and calls them from that place. Nothing more. Well, if your mishmash works for you - good, but I have suspicion that something is wrong in your scheme. Try to encode some WAV file with latest Nero installed on your machine and then encode the same file with Audition. Decode resulting files with some decoder and compare the audio data from both decoded files to see if they're identical.