Judging by your description it doesn't sound like the hub. Would you describe it as an intermittent squeak or a more prolonged screech? Does it correlate it to any specific situation like bumps, turning etc? Can you reproduce it by compressing the fork manually (off the saddle) and perhaps rolling the bike fore and aft? Are the brakes aligned properly and can you verify they are not contacting the tire?
Originally posted by Richard D
How water got up in the forks is the only question though - it might have ben wet this morning but I don't recall riding through anything deep...
Correct me if I'm wrong but this suspension fork has seen a lot of rain and has never been lubed/overhauled? Water will work it's way in anything given time. This sound is likely a result of a cumulative effect. If the fork is more than a few months old and you commute on it twice a day it is quite possible it needs attention. What kind of fork is it? Roughly how many miles?