just a FYI,
Mac OS X 10.10.3 was throwing the error below. I didn't find much just googling around and wanted to post what fixed the issue in my case.
5/4/15 6:30:18.410 AM networkd: -[NETProxyLookup pacLookupComplete:proxies:error:] PAC evaluation error: Error Domain=kCFErrorDomainCFNetwork Code=308 "The operation couldn’t be completed. (kCFErrorDomainCFNetwork error 308.)"
The cause was a mal-formed PAC file. Our network admin accidentally put a parentheses inside a quote. The system completely disregarded the proxy until the syntax error was fixed.