For al those of you having problems with your USB flash disks especially if you get the error "device /dev/sda1 is not a valid block device" when mounting, I have a solution. I have a Transcend Jetflash USB 2.0 memory stick which works under windoze but until recently wouldn't work in linux.

I have been trying to get my USB Flash disk to work in linux for a long time and finally succeeded. if your flash disk is seen by linux but just will not mount it is probablt a problem with the partitions and the scsi emulation, since i gather that usb devices are treated as scsi devices. on solution said to use fdisk /dev/sda to delete any partitions that windose creates and create a single primary partition. and then make this a vfat partition using "mkdosfs". I was about to try that when my USB Flash disk miraculously began to work last night. this was after i had installed the sg3-utils. the sg3 utilities are a set of scsi related utilities that seem to now allow me to mount my disk with all the partitions the windoze has stupidly put on. unfortunately slackware 10 didn't come with it so i had to download it and compile it but this didn't take long at all. so now i have a working USB Flash disk.

so as long as the output of dmesg says your flash stick has been connected to a certain usb port and doing "less /proc/scsi/usb-storage/1" shows you the details of ur flash stick, installing sg3-utils should work.

also something i found out along the way is that windoze treats a flash stick as a floppy device so it doesn't have a proper partition table. this also means that if ur having problems mounting it to /dev/sda1 then u should rather be trying to mount it on /dev/sda coz thats where usb floppy drive get mounted.

hope this helps and that u are able to get ur flash stick working.