i had/have a similar problem and after selecting format from the drop box on "removable disk" or how ever your computer registers it, i selected FAT32 and let it run for about a minute, the drive was blank and the problems you listed were resolved, i had to do that imediatatly, it also dose AMV clips and it seems unable to cope with mutiple media formates, that may have been a per-existing condition.
i recomend formatting in FAT 32, and treating it like new. because it is an ipod, worst case scenario is you need to reinstall your firmware after formatting, you probably wont need to. first you need to download the updte software, and from apple.com you can get the firmware. you need a specil program to add the firmware...while there you should upgrade anyway. if apple dose not have the app. to install the firmware i do, E-mail me at True.knowledge@yahoo.com and i can send it to you.
zane abdelbagi, March 2008