That was not the first time i did see this, and i’m sure will not be the last. So i will leave here for future references…
After a restart, one OpenSolaris host (2009.06 dev), the link /dev/msglog was gone. Many services in maintenance state, but no problem just recreate it… no way. The devfsadm command or directly issuing: ln /devices/pseudo/sysmsg@0:msglog /dev/msglog did return “cannot create”. I did remember that same case with the /dev/null but the problem was in “/etc/security”. But “googling” for /dev/null cannot create i came to this post, and here i did put the solution (tks Nils Goroll):

cd /; mkdir dev.new
cd dev ; find . | cpio -dump /dev.new
mv dev dev.old && mv dev.new dev
devfsadm

peace