16 bit 44.1 via USB "file not recognized"???

First off im sure this has been asked so my bad on the new thread but im going crazy on this!!
Here's my story: Ive been an MPC user since my old 2000xl. I ended up copping a 2500 and LOVED it. I ended up catching a case and did a couple years in the joint. In the meantime, my BABY, my 2500 (that was fully kitted out, max ram, dvd burner, extremely well maintained, you know the deal) got jacked by my supposed partner . Now, Im home and trying to get it back together. Getting money slow and legal all I have is a 500, an old laptop and an external harddrive full of samples and .pgm's etc.
So NOW, I'm trying to simply load the samples into the 500 like i used to do with the 2500 and its nothing but headaches.
I've made sure that the samples are .wav 16 bit 44.1 and theyre STILL not recognized!!?? WTF??? Im using adobe audition to edit the samples on the laptop. I convert sample type to 16 44.1 mono. That should be enough am I wrong?
PLEASE PLEASE bless me with some knowledge to help me on this..
Thank you all ahead of time...peace

Are you sure that the name of the sample are not lot longer then 16 characters?

This happens to me quite often. Now I always convert everything to .wav (yes even if its 16 bit wav @ 41000 khz) with AOA free audio convertor before I bother to load it into the mpc.

Thanks to everyone who replied. I'm gonna try all those. Good looking on the converter. I've been peoccupied lately with a bunch of samples etc I found on a harddrive o used with the2500. They all work great and it's been fun reworking old projects and freaking the samples in a new way.. Thanks again