Do you have a Mac still running Tiger (Mac OS 10.4)? And did you recently decide to install a PEAR component for use with some PHP? And lastly, did it fail with some cryptic HTTP error "410 Gone" that you had very little luck finding with Google? I did.
The solution is a bunch of steps backward and then forward again. Unfortunately, it's not very clear to the perhaps large number of Mac users who did not keep their PEAR libraries up to date all along on Tiger. But the answer is here, at the moment (it will scroll off when more news is added): http://pear.php.net/