The test box I was running on was power-cycled over the weekend (more than once) and now zimbra/ldap doesn't start. I've dug around the forums a little but can't see this exact problem being replicated.
The basic error I'm seeing is :
From digging around some other threads I tried running slapd by hand with debug on and get the attached output. I'm guessing that the berkeleydb files are corrupt in some way? Maybe....
db_recover: Finding last valid log LSN: file: 1 offset 2792480
db_recover: Recovery starting from 
db_recover: Recovery complete at Tue Jan 31 11:53:38 2006
db_recover: Maximum transaction ID 8000000b Recovery checkpoint 
ERROR - failed to start slapd