[fetchmail] incorrect header line found while scanning headers

I have several fetchmail servers at customer's sites  The fetchmail software
is up-to-date (6.2.2+NLS). I'm noticing that a lot of mail is not getting
flushed off my isp's server. It looks like it's all junk mail but fetchmail
has to handle it every time it does a fetch. Here's what a piece of the log
looks like:

fetchmail: POP3< 46 2964
fetchmail: POP3< 47 8867
fetchmail: POP3< 48 1961
fetchmail: POP3< 49 4564
fetchmail: POP3< 50 8653
fetchmail: POP3< 51 6100
fetchmail: POP3< .
fetchmail: POP3> RETR 1
fetchmail: POP3< +OK
fetchmail: reading message danton(_at_)pop3(_dot_)nac(_dot_)net:1 of 51 (6703 
octets)
fetchmail: incorrect header line found while scanning headers
fetchmail:  retained
fetchmail: POP3> RETR 2
fetchmail: POP3< +OK
fetchmail: reading message danton(_at_)pop3(_dot_)nac(_dot_)net:2 of 51 (4248 
octets)
fetchmail: incorrect header line found while scanning headers
fetchmail:  retained
fetchmail: POP3> RETR 3
fetchmail: POP3< +OK
fetchmail: reading message danton(_at_)pop3(_dot_)nac(_dot_)net:3 of 51 (9657 
octets)
fetchmail: incorrect header line found while scanning headers
fetchmail:  retained
__________________________________


My fetchmail -V looks like:

This is fetchmail release 6.2.2+NLS
Fallback MDA: (none)
Linux mail.ourdomain.com 2.2.16 #1 Mon Oct 30 09:43:59 EST 2000 i686 unknown
Taking options from command line and /root/.fetchmailrc
Logfile is /var/log/fetchmail
Idfile is /root/.fetchids
Fetchmail will forward misaddressed multidrop messages to postmaster.
Options for retrieving from US(_at_)isp(_dot_)mail(_dot_)server:
  True name of server is our isp.
  Protocol is POP3.
  All available authentication methods will be tried.
  Server nonresponse timeout is 300 seconds (default).
  Default mailbox selected.
  All messages will be retrieved (--all on).
  Fetched messages will not be kept on the server (--keep off).
  Old messages will not be flushed before message retrieval (--flush off).
  Rewrite of server-local addresses is enabled (--norewrite off).
  Carriage-return stripping is disabled (stripcr off).
  Carriage-return forcing is disabled (forcecr off).
  Interpretation of Content-Transfer-Encoding is enabled (pass8bits off).
  MIME decoding is disabled (mimedecode off).
  Idle after poll is disabled (idle off).
  Nonempty Status lines will be kept (dropstatus off)
  Delivered-To lines will be kept (dropdelivered off)
  Messages will be SMTP-forwarded to: localhost (default)
  Recognized listener spam block responses are: 451 571 550 501 554 553 551
  Multi-drop mode: 1 local name(s) recognized.
  DNS lookup for multidrop addresses is disabled.
  Envelope header is assumed to be: Received
  Predeclared mailserver aliases: worldnet.att.net
  Local domains: mrcdi.com
  No UIDs saved from this host.
____________________________________________

Please Help