unclean unmounting of / on shutdown

[swood]

Hi All, 

I've started getting an error causing the root file system to not be properly
unmounted on a shutdown or reboot. I get an error like;

 "device / busy    [Failed]" 
or 
"file system / busy   [failed]"

This is happening at the end of the  shutdown or reboot sequence and causes a
forced check of the file system on power up.

I'm stumped. Can any one give some suggestions as to what could be causing this
problem.

Stuart