Go to Virus Scan Console right click on Access Protection and go to properties. Go to Common Standard Protection. (dropbox is weird and runs the dropbox.exe from the application data folder in the users profile) Under all the ones with check marks add dropbox.exe to excluded.
http://kuzba.com/wp-content/uploads/2011/08/mcafeedropbox1.jpg
http://kuzba.com/wp-content/uploads/2011/08/mcafeedropbox2.jpg
Do that for everyone with a checkmark. People use it and
I’ve had to do this in the past. Given they are all on 8.8 I am sure that
other users will run into issues where drop box stops working for no apparent
reason however the reason is mcafee.