Nero wav-mp3 conversion problem

I am using Nero 6.6.0.12 with a licensed mp3 pro add in to convert .wav files to mp3 format. I have never had any difficulty doing this before. However, I have just struck a series of .wav files that Nero won’t convert. I just get the message “can’t encode file”. I can’t make any sense of it. I have checked to make sure that it isn’t a general problem by ripping a couple of tracks from a CD to wav format and then encoding them to mp3, and didn’t have any problems.

I can covert the problem files to wma and to mp4 format using Nero, but not to mp3. Once I have converted the files to mp4 I can then convert them back to mp3. But this is a hassle and I seem to lose quality in the process, and the originals are pretty poor to start with.

I have tried converting the same files to mp3 format using Total Recorder and dbPowerAmp - no problems - but Nero usually does a better job more easily than these programs IMHO

The problem files were originally .aa files from Audible.com (legally purchased) and converted to wav format using dbPowerAmp. I have never had difficulty before converting this sort of file to mp3 with Nero 6. To make sure, I have just downloaded another .aa file from Audible, converted it to wav using dbPowerAmp and then converted it to mp3 using Nero - no problems. (You may ask - why not convert it directly to mp3 using dbPowerAmp? In my experience I don’t get anything like the same quality as converting to wav and then to mp3 using Nero.)

So, there must be something particular about these problem files that Nero doesn’t like. But I have no idea what it might be.

The files are of an old audio book and the quality is pretty poor. They are mono, 8KHz, 16 bit, 128 kbps, PCM.

Can anyone suggest what might be going on here? :confused: