store.log oddity (with Squid 2.1.PATCH2)

My script for summarising store.log (just the rate at which data is being
written to or read from the cache, nothing fancy) is complaining
intermittently about invalid log entries from Squid 2.1.PATCH2 such as

919951056.578 SWAPOUT 003995C7 200 919951051 -1 -1 -1/448
GET http://www.ambafrance.org.uk/attach.phtml?

(one line split for readability).

The problem is that the content-type field (which should appear between
the last "-1" and "-1/448") is missing. Most log entries are OK (maybe 4-5
with this problem yesterday in a 200MB log file), but some have the problem.
It is not (or should not be) something as simple as "server didn't send
content type", as Squid normally logs "unknown" in that case (judging by
other log entries).

Anyone else seen this? Anyone worked out why it happens or how to fix it?

                                John Line

-- 
University of Cambridge WWW manager account (usually John Line)
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