I've noticed a problem using pure-ftpd with large file support on the latest gentoo. When a download of a large file reaches almost 4GB it aborts the transfer and the user is unable to resume that transfer, ftpd gives: "Unable to map the file into memory: Invalid argument". I didnt have any problems with this with previous versions and i have tried downgrading but it didnt help so my guess is that its something else causing the problem (glibc?).
Sorry, was a problem with my kernel. /Andreas