It tries a few times, failing each time, as below.
[root@mail /]# freshclam
ClamAV update process started at Thu Apr 12 15:42:03 2012
main.cld is up to date (version: 54, sigs: 1044387, f-level: 60, builder: sven)
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 193.1.193.64)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 116.240.207.20)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 117.104.160.194)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 193.1.193.64)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 116.240.207.20)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: Incremental update failed, trying to download daily.cvd
Downloading daily.cvd [100%]
[LibClamAV] ***********************************************************
[LibClamAV] *** This version of the ClamAV engine is outdated. ***
[LibClamAV] *** DON'T PANIC! Read http://www.clamav.net/support/faq ***
[LibClamAV] ***********************************************************
WARNING: Mirror 193.1.193.64 is not synchronized.
Trying again in 5 secs...
ClamAV update process started at Thu Apr 12 15:43:18 2012
main.cld is up to date (version: 54, sigs: 1044387, f-level: 60, builder: sven)
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 116.240.207.20)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 117.104.160.194)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 193.1.193.64)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 116.240.207.20)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: getfile: daily-12639.cdiff not found on remote server (IP: 117.104.160.194)
WARNING: getpatch: Can't download daily-12639.cdiff from db.local.clamav.net
WARNING: Incremental update failed, trying to download daily.cvd
Downloading daily.cvd [100%]
[LibClamAV] ***********************************************************
[LibClamAV] *** This version of the ClamAV engine is outdated. ***
[LibClamAV] *** DON'T PANIC! Read http://www.clamav.net/support/faq ***
[LibClamAV] ***********************************************************
WARNING: Mirror 193.1.193.64 is not synchronized.
Trying again in 5 secs...
ClamAV update process started at Thu Apr 12 15:44:32 2012