I just tried it and it was OK here. Try a different mirror?

zippy:~/projects/tmp$ wget http://search.cpan.org/CPAN/authors/id/G/GA
+/GAAS/MIME-Base64-3.07.tar.gz
...
zippy:~/projects/tmp$ tar xfz MIME-Base64-3.07.tar.gz
zippy:~/projects/temp$ ls -l
total 24
drwxr-xr-x 3 xxx xxx  4096 Nov 30  2005 MIME-Base64-3.07
-rw-r--r-- 1 xxx xxx 15548 Nov 30  2005 MIME-Base64-3.07.tar.gz
...
[download]