If you didn't specify another prefix for Perl 5.10.x modules when you compiled the new version, you're probably re-using the same module installation paths between Perl 5.8.x and 5.10.x, in which case you now have two broken Perl installations. Pure-perl modules should be fine, but XS components are different between the two major versions.

You need to reinstall the system Perl and then reconfigure and recompile 5.10, giving it a different installation path.