You should probably include a bit more specific information, as there can be many different factors involved here.
For instance, what file type / bit rate are the originals, and what settings did you use to save them? Whether ripped from an audio cd, copied from an mp3 file, or recorded from streaming audio with SoundTap or Golden Records, you usually have the option of choosing the file type and attributes.
Then you must choose the proper file type and attributes when saving your edited file in WavePad, which may depend on whether you want to burn an audio cd, or transfer files to an ipod.
And how are you listening to the playback (after saving the edited WavePad file) – sometimes I have experienced poor sound quality due to some conflicting software issues on my computer, but the file itself was actually ok.