Problem with export db at shutdown

[stitch at power.ms]

Hi!

Cause of a longtime power failure i had to shutdown our mail server.
During 
"service cyrus-imapd stop"
 the system hangs at exporting the database
soi had to reset the system.

After reboot i did "ctl_cyrusdb -r" as user cyrus.
DB recoverd sucessfully

for tests i restart cyrus-imapd, and also hanging , see ps fax:

5567 ?        S      0:00 /bin/sh /usr/lib/cyrus-imapd/cvt_cyrusdb_all export
5625 ?        D      1:09 /usr/lib/cyrus-imapd/cvt_cyrusdb /var/lib/imap/deliver.db berkeley /var/lib/imap/deliver.db.skiplist skiplist

5625 is dead and server hangs

DO anybody know a solution ?

Thanks

Georg