Then my next guess is a problem regarding access rights. (I hate this stuff since the time, it was invented on DEC/VMS) I would try to give 777 to all files/dirs, which are used by squid.
OR (not so brutal) start squid with full debug using squid -X -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Upgrading-SQUID-from-3-1-6-to-3-1-23-tp4659259p4659345.html Sent from the Squid - Users mailing list archive at Nabble.com.