Infrarecorder Issue

Anyone use Infrarecorder, fire up an audio CD project, then try to add MP3 files and get an error that says "The file you are trying to add is not supported."

There's a number of strange things that involve this issue. I am running Infrarecorder 0.46. I installed K-Lite's latest Mega Codec Pack. I've downloaded the Infrarecorder MP3 plug-in and placed it into the Codecs folder. I've uninstalled and backdated Infrarecorder to version 0.45. I've used versions 0.41 and 0.42 of the MP3 plug-in. And time and time again, I would add an MP3 file to an audio track and the same error would come up saying that the file is not supported. The funny thing is, I'll add another MP3 file and somehow that makes it into the list with no problems. The MP3 files are all of the same audio sample rate (44 kHz), all stereo (2-channel), and some of them vary in bit rate (anywhere from 128 to 320 kbps). This machine is running Windows XP Professional with SP2.

Even stranger, I have my laptop at home, running Infrarecorder 0.45, with no MP3 plug-in, running Windows Professional with SP2, and I have no problems, whatsoever. I can add MP3s to audio projects with no problem.

For the record, I'm not looking for any alternative programs to use, if that's what you're going to throw at me for a solution.

Can anyone explain why this occurs and how I fix this, or what to look for?