Are we dealing with the same version?
mount gives me:
/dev/sdc on /media/SANSA CLIPP type vfat (rw,nosuid,nodev,noatime,uhelper=hal,shortname=lower,uid=500,flush,utf8)
using /dev/sdc or /dev/sdc1 gets the same response:
# mlabel -i /dev/sdc1 :"Howards Clipp"
Mtools version 4.0.17, dated June 29th, 2011
Usage: mlabel [-vscVn] [-N serial] drive:
I think the double colon in your message must be a typo?