Hey James,
Do you already have an instance of apache running? OSX ships with apache, I think you can turn it on accidentally by enabling web sharing or something along those lines--sorry I don't have 10.6. All apache installations run on port 80 by default, and you can get a slightly cryptic error similar to what you are seeing (not rocking damp here so I am only guessing).
As far as damp vs xampp, I'm sure damp is a great product and probably has some nice drupal integrations. You can run drupal on any stack tho--I've had good success setting people up with MAMP. So trying another stack may resolve things or at least help you figure out if your issues are application specific.
Debuggers can be a little tricky--there's a nice vim php debugger guide you can easily google for. I wouldn't recommend the vim route if you aren't already familiar with vim tho. Other than that, I believe eclipse has support for debugging integration.
Best,
Tim
Tim Loudon
t: 781.686.6096
Thanks Daniel, Michael, Moshe. It seems like a combination of working through the issue queues and using a step-through debugger is probably the best way to proceed.
For the record I'm going to try
http://robshouse.net/article/xdebug-komodo-and-acquia-drupal-stack-installer. I'm going to use it with XAMPP rather than the Acquia DAMP stack through (I can't actually get Acquia DAMP to install on my Mac - see
http://acquia.com/node/911603 - any tips?). Does the Acquia stack have any particular advantages?
Thanks once more, I'm off to set up a debugger. Wish me luck!