Why are you using XP for Struts development when you have a Unix environment already in OS X?
Download eclipse into Mac OS X and develop using it. The Tomcat executable for Unix runs seamlessly on OS X without any changes required, but you can build it from source if you want to be really sure it'll work.
500 responses in my experience are due to errors in the application - for instance a NullPointerException when trying to access a method of a null object will filter up to the page displayed to the user unless you take steps to catch the error. Check the Tomcat logs for errors.
A 401 response means Not Authorized.
I don't think any of this is a Parallels problem.
I have a Linux VM running a Struts webapp with Tomcat - much of which was developed on Mac OS X. I run it in Linux because that's the final destination for my code ... a Linux server, but development on OS X was as easy if not easier than in Linux. Webapp development in Windows XP is an utter pain. Avoid it like the plague.
Last edited: May 16, 2006