Problem mounting second disk

[John]

I have a disk at /dev/hdc that was not present when I installed Warty.

As the Warty kernels do not work (separate thread), I'm running 
2.6.8-1-k7 from sarge.

/dev/hdc detects and I can read its partition table and test its speed 
with hdparm.

What I cannot do is mount it:
summer at Glider:~ $ grep hdc /etc/fstab /proc/mounts; sudo bash -c 'rmdir 
/mnt/hdc5;mkdir /mnt/hdc5;strace -f -F -o /tmp/mount.trace   mount 
/dev/hdc5 /mnt/hdc5'
Password:
mount: /dev/hdc5 already mounted or /mnt/hdc5 busy
summer at Glider:~ $ sudo fdisk -l /dev/hdc

Disk /dev/hdc: 120.0 GB, 120033041920 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

    Device Boot      Start         End      Blocks   Id  System
/dev/hdc1               1           6       48163+  83  Linux
/dev/hdc2               7           7        8032+   1  FAT12
/dev/hdc3               8         505     4000185   83  Linux
/dev/hdc4             506       14593   113161860    5  Extended
/dev/hdc5             506       14593   113161828+  83  Linux
summer at Glider:~ $


Here are the interesing bits from the trace:
summer at Glider:~ $ grep -1 /dev/hdc5 /tmp/mount.trace
25102 execve("/bin/mount", ["mount", "/dev/hdc5", "/mnt/hdc5"], [/* 25 
vars */]) = 0
25102 uname({sys="Linux", node="Glider", ...}) = 0
--
25102 rt_sigprocmask(SIG_BLOCK, ~[TRAP SEGV RTMIN], NULL, 8) = 0
25102 stat64("/dev/hdc5", {st_mode=S_IFBLK|0660, st_rdev=makedev(22, 5), 
...}) = 0
25102 open("/dev/hdc5", O_RDONLY|O_LARGEFILE) = 3
25102 _llseek(3, 0, [0], SEEK_SET)      = 0
--
25102 close(3)                          = 0
25102 mount("/dev/hdc5", "/mnt/hdc5", "ext3", 0xc0ed0000, 0) = -1 EBUSY 
(Device or resource busy)
25102 rt_sigprocmask(SIG_UNBLOCK, ~[TRAP SEGV RTMIN], NULL, 8) = 0
--
25102 open("/usr/share/locale/en_US/LC_MESSAGES/util-linux.mo", 
O_RDONLY) = -1 ENOENT (No such file or directory)
25102 write(2, "mount: /dev/hdc5 already mounted"..., 51) = 51
25102 umask(077)                        = 033
summer at Glider:~ $


Is there any alternative interpretation of EBUSY?

Does anyone have any ideas?

I've tried stopping suspects includng fam, evms, lvms and md*.

Oh, I can e2fsck the paritions so those aren't busy. I don't see how a 
brand-new mount point can be busy.