upgrade 2.0.16 to 2.1.16 - ctl_cyrusdb hangs

[Sam Smith]

The upgrade seemed to go OK, but when I start the master process it 
starts ctl_cyrusdb. I get the following messages:

Dec 17 14:16:05 newimap.ece.gatech.edu master[9932]: [ID 392559 
local6.debug] about to exec /usr/cyrus/bin/ctl_cyrusdb
Dec 17 14:16:05 newimap.ece.gatech.edu ctl_cyrusdb[9932]: [ID 702911 
local6.notice] recovering cyrus databases

and that's all. ctl_cyrusdb never seems to finish recovering, imapd 
never starts, etc.

We do have over 100G of email... Should ctl_cyrusdb take hours?

Sam Smith