OK...got a new one.
For some reason I've lost part of my exchange sync account somehow...I don't have any of my exchange contacts or calendar, but email is still working.
I tried adding the account again (it's not listed in Settings>Accounts) but get the error message that the account already exists.
I went into Manage Apps and cleared data for the email app and email engine, and then tried to add the account again - still says the account already exists...
Appreciate any pointers on whether I can separately clear the "ghost" corporate sync account that is no longer functional, or if I'm going to have to wipe data...
I have a recent clockwork backup, so I may just restore that...but would be good to know how to resolve this in a more targeted way if it happens again.
"Ghost" has happened to me when I clear app data while still logged into it, only way to fix is to restore a backup or reflash.