Toshiba 2GB USB Flash Drive Capacity Problem

Question

I have a Toshibs 2GB USB Flash Drive I use on my Vista laptop. I have formatted the drive which shows a 1.85GB capacity remaining however will not allow me to put any more than 450MB in data before telling me the drive is full and preventing me from transferring any more files. At this point the drive properties stll show the remaining 1.5GB as free space however I can not transfer any more files. How can I access the remaining 1.5GB?