On my local usemod wiki, when I try to submit the preferences form, I get this reply:
Invalid UserID 111, preferences not saved. (Preferences require cookies, but no cookie was sent.)
I need help with diagnosing what the problem could be.
I'm using UseMod 1.0 (SlashLinks disabled) with Firefox 22.214.171.124 on Mac OS X 10.4.5 (in the usual manner, just dropped wiki.pl in the cgi-bin directory of the preconfigured Apache that came with the OS), have cookies enabled, and indeed I have one cookie for the correct site (127.0.0.1) and with the correct name, so it should definitely be sent and also be recognised by the wiki. Unfortunately I haven't paid attention to my username or preferences in a long while, and 'recent changes' shows I've been editing as 'localhost' (instead of 'myusername') for all of the last 96 days (the maximum duration I can select under recent changes), so it's impossible to tell when the cookie stopped working and which change could be the cause.
$cookie .= ";expires=Fri, 08-Sep-2013 19:48:23 GMT";