Well there's several general availability releases of 4.5.x - but that sounds like 4.5.0?
Check your /opt/zimbra/.install_history file.
Do you have issues on other zmcontrol or zmprov commands or just that one?
You can also type $set:get version in your AJAX web-client main search bar.
Reasons to go to 4.5.11 first:
-Large changes to Tomcat & LDAP around the 4.5.5/.6/.7/.8 area. For instance 4.5.2 > 5.0.8 is a big jump - while we test upgrading from everything in the 4.5.x line (that's different than 4.0.x line) by very definition there were more 4.5.8+ upgrades to 5.0.x 'ran' as that was current was when some of the 5.0.x beta's came out.
-If you have any LDAP replicas you definitely should.
LDAP Replicas 4.5.x to 5.0.x - Zimbra :: Wiki
Make sure everything's fine, backup again, upgrade to 5.0.8 (no need to run through all the 5.0.0.1/.2/.3/.4/.5/.6/.7)
4.5.11 (02/01/08)
4.5.10 (11/21/07)
4.5.9 (10/22/07)
4.5.8 (10/04/07) FOSS
4.5.7 (09/18/07)
4.5.6 (06/28/07)
4.5.5 (05/06/07)
4.5.4 (03/28/07)
4.5.3 (03/01/07)
4.5.2 (02/16/07)
4.5.1 (02/05/07)
4.5.0 (01/16/07)
4.5.0 RC2 (01/06/07)
4.5.0 RC1 (12/15/06)
4.5.0 Beta2 (07/24/06)
4.5.0 Beta1 (06/26/06)