[Dovecot] Corrupted index cache file and Maildir filename has wrong W value

[Barry Scott]

kmail stopped working and when I check the dovecot log file I see:

May  4 11:40:38 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/._NewMail-com/dovecot.index.cache: Corrupted virtual size for uid=234: 633278 != 633251
May  4 11:40:38 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/._NewMail-com/dovecot.index.cache: Corrupted virtual size for uid=234: 633278 != 633251
May  4 12:34:44 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/.Mailing Lists.Xorg Devel 2010-04/dovecot.index.cache: Corrupted virtual size for uid=312: 8884 != 8858
May  4 12:34:44 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/.Mailing Lists.Xorg Devel 2010-04/dovecot.index.cache: Corrupted virtual size for uid=312: 8884 != 8858
... more of the same...
May  4 13:02:54 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/.Mailing Lists.Xorg Users 2010-04/dovecot.index.cache: Corrupted virtual size for uid=38: 30392 != 30366
May  4 13:02:58 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/.Mailing Lists.Xorg Users 2010-04/dovecot.index.cache: Corrupted virtual size for uid=43: 8796 != 8770
May  4 15:25:03 f12barry dovecot: IMAP(bscott): FETCH [] for mailbox _NewMail-com UID 48 got too little data: 3230 vs 3278
May  4 15:25:03 f12barry dovecot: IMAP(bscott): Maildir filename has wrong W value: /home/bscott/Maildir/._NewMail-com/cur/1271683097.M615087P3538.f12barry.office.onelan.co.uk,S=3154,W=3278:2,S
May  4 15:25:03 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/._NewMail-com/dovecot.index.cache: Broken virtual size for mail UID 48
May  4 15:25:03 f12barry dovecot: IMAP(bscott): Disconnected: FETCH failed bytes=15437134/33737060
May  4 17:45:41 f12barry dovecot: dovecot: Killed with signal 15 (by pid=7300 uid=0 code=kill)

At this point I had only tail'ed the log and seen the issue with UID 48.
I then:
1. stopped dovecot
2. deleted the ofending file
3. deleted the dovecot* files
4. started dovecot

May  4 17:49:58 f12barry dovecot: Dovecot v1.2.11 starting up (core dumps disabled)
May  4 17:52:17 f12barry dovecot: Killed with signal 15 (by pid=7556 uid=0 code=kill)
May  4 17:53:21 f12barry dovecot: Dovecot v1.2.11 starting up (core dumps disabled)
May  4 17:53:21 f12barry sendmail[2067]: starting daemon (8.14.3): SMTP+queueing at 01:00:00
May  4 17:53:21 f12barry sm-msp-queue[2075]: starting daemon (8.14.3): queueing at 01:00:00
May  4 17:55:26 f12barry dovecot: imap-login: Login: user=<bscott>, method=PLAIN, rip=::1, lip=::1, secured
May  4 17:55:29 f12barry dovecot: IMAP(bscott): FETCH [] for mailbox _NewMail-com UID 48 got too little data: 3878 vs 3920
May  4 17:55:29 f12barry dovecot: IMAP(bscott): Maildir filename has wrong W value: /home/bscott/Maildir/._NewMail-com/cur/1271683097.M733325P3538.f12barry.office.onelan.co.uk,S=3780,W=3920:2,S
May  4 17:55:29 f12barry dovecot: IMAP(bscott): Corrupted index cache file /home/bscott/Maildir/._NewMail-com/dovecot.index.cache: Broken virtual size for mail UID 48
May  4 17:55:29 f12barry dovecot: IMAP(bscott): Disconnected: FETCH failed bytes=3955/48628
May  4 18:05:55 f12barry dovecot: imap-login: Login: user=<bscott>, method=PLAIN, rip=::1, lip=::1, secured

Now another file is being complained about.

What would cause these problems?
What is the W value and how could I check it?

Here is the details of the dovecot I'm using and the kmail version I'm using.ƀ

$ sudo dovecot -n
# 1.2.11: /etc/dovecot.conf
# OS: Linux 2.6.32.11-99.fc12.x86_64 x86_64 Fedora release 12 (Constantine) 
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/lib64/dovecot/imap
mail_plugin_dir(imap): /usr/lib64/dovecot/imap
mail_plugin_dir(pop3): /usr/lib64/dovecot/pop3
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd

Client is kmail from kdepim-4.4.2-1.fc12.x86_64

Barry