Unable to delete files from USB

I have seen multiple issues resolved by formatting or changing the policies to optimum performance. However, this does not work for me.
I am currently using Lexar 8GB USBs. When plugged in they flash repeatedly notifying me that the disk is full. They were originally formatted FAT32 default.
When I try to delete an old file I am prompted with:
"An error has occurred the destination you have specified does not exit. it might be an offline network location or an empty CD or DVD Drive. Check the location and try again"

I am unable to copy, edit, move, or delete files and am also unable to reformat the usb. On top of that, when I try to do any of these options it will prompt the error message and then disconnect the drive.

Any help would be appreciated.
Thanks