Is het een Ipod Touch?
EDIT: Ik heb even wat voor je opgezocht waar je wat aan kan hebben:
hi all?
i've seen some of you guys struggle with the same problem as i do: mp3 playback over usb gets interrupted by error msgs. well, i tried to isolate the problem. here are my findings:
first i tought it might come from corrupted/damaged/weird formatted mp3's, and in that case a buggy mp3-decoding engine. this seems not to be the case. also VBR and CBR mp3s encoded mp3s work nicely at all rates (up to 320kbps)
the problem seems to be the filesystem-handler of the cdj-400, which is capable of reading FAT and FAT32 filesystems.
the problem (eg. error E-8304) seems to occur then the filesystem handler is unable, or at least unable in a certain aount iof time, to retrieve data from the USB device. in my case this has been USB flash sticks.
now you have to understand that every filesystem gets fragmented as longer as you work on it. (also usb sticks therefore!) a fragmented filesystem means in reality that the data is more scattered (non concatinated) over the device, and therefore requites more IO's to the device to be fully retrieved. more IO's mean more time, and in the end it can be treated as a delay. so, to put this one more understandable, it seems that the CDJ is running into filesystem-read timeouts and pops errors.
now what did i do to solve this?
i copied all mp3s from my sticks to my computer, and reformatted the sticks (using quick format is OK).
i reformatted using the FAT32 filesystem (instead of the old FAT filesystem that had been on the sticks) and recopied all mp3's back to the sticks. and guess what

NO MORE ERRORS!..
i hope this is also useful for you guys out there, until the firmware updates arrives.
cheers