When I try starting Apache from the XAMPP control panel (Mac OSX Snow Leopard), I get the following error popup and Apache won't start:

/Applications/XAMPP/xamppfiles/bin/apachectl: line 70: ulimit: open files: cannot modify limit: Invalid argument
(48)Address already in use: make_sock: could not bind to address [::]:80

XAMPP was running perfectly 10 minutes earlier. I stopped Apache to add some .conf files and it failed on restart. I removed all the new .conf files (i.e. reverted it to how it was before) but now I get the above message.

EDIT: I've checked AppMonitor and I see the "httpd" processes (one by _www nested within root). Just tried quitting these but they're auto-restarted on new process IDs and it didn't solve the problem.