Taalaibek Ashirov wrote at 18:40 +0300 on Sep 10, 2008:
 > On Wed, 2008-09-10 at 09:20 -0600, John Hein wrote:
 > > John Hein wrote at 08:23 -0600 on Sep 10, 2008:
 > >  > Out of curiosity, what is the output of 'df /var/log/amanda/dotProject'?
 > > 
 > > And the output of mount.
 > 
 > web# df -h /var/log/amanda/dotProject/
 > Filesystem     Size    Used   Avail Capacity  Mounted on
 > /dev/da0s1a     30G     12G     16G    43%    /
 > web# mount
 > /dev/da0s1a on / (ufs, local)
 > devfs on /dev (devfs, local)
 > /dev/da1s1d on /home (ufs, local, soft-updates)
 > /dev/da0s1d on /tmp (ufs, local, soft-updates)
 > linprocfs on /usr/compat/linux/proc (linprocfs, local)

Since that's plain old ufs, that rules out issues with wonderful and
exotic filesystems.

What happens when you compile and run this (as the backup user)?

#include <err.h>
#include <fcntl.h>
#include <stdio.h>
int
main()
{
    struct flock lock;
    int fd = open("/var/log/amanda/dotProject/foo", O_RDWR | O_CREAT);
    if (fd < 0) err(1, "open");

    lock.l_type = F_WRLCK;
    lock.l_whence = SEEK_SET;
    int r = fcntl(fd, F_SETLKW, &lock);
    if (r < 0) err(1, "fnctl");
    return 0;
}