sound problems after authoring with dvdlab pro

[dyln]

hi everyone...i have many dvd video clips of family birthdays, weddings ,xmas etc and i want to put them onto 1 dvd disc with menus linking to each differant occasion but the audio noise level on the dvd's are all at differant levels and i want make them all the same.
everything is going great until i check the finished dvd in powerdvd before burning it to disc but when i author the final multi dvd with dvdlab pro there is no sound from any of the dvd video clips when i watch them in powerdvd.
all video clips are working great in powerdvd before i author it and i get no error messageswhen i click on 'compile dvd' in dvdlab pro.
however if i author the same files with tmpgenc dvdauthor it works great but i would rather use dvdlab pro cos i can make much better menus.
i am working originally from vob files and am only trying to normalise the sound level before authoring to make a new multi dvd.
this is what i am doing so far with the software i have availble to me...

1 demutiplex original vob file with vobedit
2 normalise movie vob file with dvd audio extractor and save as mp3 mpeg1 Layer lll
3 change the new mp3 mpeg1 Layer lll file into an ac3 file using
Xilisoft video to audio converter and rename it to the same as the m2v file if needed
4 author new dvd with ifoedit using the m2v file from #2 and the ac3 file from #4 and save the new dvd files in a new folder
5 check new dvd movie in powerdvd to make sure it plays ok

REPEAT ABOVE FOR EACH MOVIE CLIP

6 if everything is ok author new multi dvd with menus in dvdlab pro
7 check multi dvd files in powerdvd and burn if everything is ok

everything works great till AFTER i have done #6
i have backed up lots of original dvds that i have to make multi dvds
(just to save space) with dvdlab pro and i have not had this problem before.
anyone got any help/advice as it would be very much appreciated
thanx dyln

[guns1inger]

I would convert the audio to wav for normalising, simply because mp3 always butchers the audio, regardless of bitrate.

Questions;

1. Are all the audio tracks the same ? (same number of channels, same bitrate, same format)

2. Do you author with multiple titlesets, or all in a single titleset ?