Problems with uploading music to PSP (expert only please)?

I've been using psp for a long time and recently got a 4 GB Sony MS Pro Duo and decided to put most of my music into it. While I was uploading the music, some of the folder show up as "0 track". Once that happen, everything else I added would become 0 track. I've done some experiment and found the following to be useful: 1) only drag and drop one music folder at a time 2) turnoff the power save mode, 3) get in & out of USB mode after copying 3 folders. I was able to copy about 1GB worth of music with this method until Windows hit a glitch and then all the files get corrupted afterwards. Once the files are corrupted, you are done because additional files transfer will also be corrupted. You cannot deleted the corrupted files/folders and the only option to clear them is to reformat. I use XP and firmware 3.11. I only transfer mp3 and wma. wma is enabled through internet. I can still play the uncorrupted files. I think this is a software bug. Any idea how to make uploading music easier?