Have you checked to see if there exists a file at
/usr/lib/perl5/site_perl/5.8.1/i386-linux-thread-multi already? It really looks to me like the error is that it cannot create a directory where a file of the same name already exists.
While you're at it, have you looked at line 127 of /usr/lib/perl5/5.8.1/ExtUtils/Install.pm to see if it looks goofy in any way?
Finally, what happens if you try to do a forced install via CPAN? I'm with you in that I'd really like to know why the normal install fails before I try to force anything, but it is an option.
- - arden.