Curious. I know that the author of Params::Validate and Alzabo are one and the same person.
I haven't had any strange problems (yet!) with Params::Validate. I trust you reported them to rt.cpan.org, as I know that Params::Validate is being actively maintained, and the latest release is dated April 04.
I'm Not Just Another Perl Hacker
I didn't report this to rt.cpan.org because they were all discussed on the Alzabo mailing list with discussion and Dave was already there.
Nice guy by the way. You should stop by the Minneapolis perl monger meeting sometime if you ever find yourself here at the right time.
I don't remember the specific problem in question, but now that Params::Validate uses XS internally, I'm not surprised if it occasionally produces weird errors. That said, I use it in production code all the time, and it's very widely used as a result of being required by Mason, and I don't get a lot of bug reports.