PLISTs, caches and permissions cause an unusual number of OS X problems:
MacInTouch Home Page: "After doing an 'Archive and Install' with Tiger I was having a lot of problems visiting various websites with Safari 2.0. I kept getting an error page saying that Safari had 'Lost the network connection' and gave the following error 'NSURLErrorDomain:-1005'. One of the problem websites was in fact www.apple.com.
After a ton of troubleshooting I found the solution to the problem. I had to delete my Cookies.plist. The file is located in ~/Library/Cookies. Once this file was removed all sites could be loaded again."