i have the "hisun Data Traveller" 8GB flash drive and wanted to test a few things since i just picked it up...
Googling led me here and i decided to test and see if i was having the same issues re: video files
the answer: YES - and heres what i am using as a workaround
to be clear, i tried all of the suggestions above and my 809MB .avi file wouldn't play, was producing popups labeling the file corrupted etc whenever i tried to play with WMP10, WMP6.4, Nero Player, WinAMP player, and VLC, and also had to reformat the flash drive
NOTE: i did copy a 4.35GB folder containg DVD movie files and it played just fine using Cyberlink PowerDVD6 (my drive came formatted as FAT32 so i used the folder vs an .iso)
what i did was to create a .zip file using WinRAR (i suppose any file compressor will do) and once the file was compressed i copied it to the 8GB flash drive
i have to say that although i didnt time it im sure copying that file took at least 10 minutes, maybe more, compared with a much shorter time when the file was not compressed (estimated 2 mnutes)
i browsed to the flash drive, double clicked on the .zip file, WinRAR began to 'open' the file, and once the file was open* i double-clicked on the .avi file and it played as usual in WMP10
file size was now 753MB instead of 809MB and i think in future i will try creating the compressed file using 'store' mode vs 'compressed' mode because im hoping that may reduce the copy time from the hard drive to the flash drive
*('extracted' inside the .zip file - ie. i did not extract to a directory anywhere but instead just 'opened' the .zip file)
i hope this help someone, it may even be useful for .iso and other types of files
:)