why won't certain playlists upload from my itunes to my ipod?

Try restoring your iPod. Restoring will erase the iPod's hard drive, reload the software and put it back to default settings. Once the restore is complete follow the on screen instructions and it should connect to iTunes and give you a prompt to automatically update your library onto the fresh installation: Restoring iPod to factory settings with iTunes 7

I'm also having similar problem, but I can only upload the purchased items in my library, all songs loaded fromoriginal CD won't load to Ipod... BUT I can see them and play them on my computer. Ideas?

When you ripped the CDs, what file format did you rip into? Check that it is not in WMA format, because an iPod will not play that.

I don't think it's WMA. I looked at "info" section of different albumns and there were apple (ACC) format. I had everything working (all songs played and down loaded)then bought a new extennal hard drive to store my 100Gb of songs on. After that the troubles started... I'll rip a CD again and seewhat happens.

I checked my formats... The files that don't load to my ipod are "Apple lossless audio format". The ones that do load are protected ACC audio file. Any ideas? Are files sizes to big for ipod?