Freezing Issues In Load Sample Area

I own a MPC2500LE. I put a bunch of folders that have samples on them into the hard drive using the usb transfer. The folders have sub folders, some have alot of samples. When i scroll over top of certain file folders the mpc just freezes. Also on certain wav files it wont play the sample when you press play then if you press load it says "Wrong File" HELP ME!

2 questions here before we get into ripping the os or talking about bugs.

How much ram?
What format are the samples in?

the ram is maxed out. i think its 128mb. i have one of the white mpc2500's that came out preloaded with all the upgrades. all my samples are in .wav format.

are all the samples in the rite bit rate? not all wav's are the same
you can do a batch convertion in wavlab to 16bit