Cal Evans had an issue - it involved XAMPP, PHP 5.3, PEAR and phar:
If you are installing PHP 5.3 and when you run go-pear.bat you get this: phar "C:xamppphpPEARgo-pear.phar" does not have a signature.
The short method to getting it working correctly is to update your php.ini file with a few small changes to the require_hash setting. Cal goes through the long method he took to finally get to that point - decision on the platform (XAMPP), version of PHP to use and some googling around that lead him to this and this to help resolve his problem.
It turns out that, if that's on, for security purposes it can't be overridden. Since the default is on, I had to open up my php.ini, find it and set it to off. Once it's off, everything works just fine.