What might be happening (this is just a guess) is that your ripping software is adding text data at the end of the resulting WAV file.

Text data, when pumped into an audio processor, looks like random noise and can produce a burst of static or a click.

Then, your MP3 encoder software isn't taking this extra data into account, and it is assuming that this extra data is audio information, and is encoding it into the file.

That's my guess.