I can't explain why it works in one place and not the other, but:
(assuming that's also you ;)
...might suggest something not quite right with the mod_perl part of the configuration. And, the DBI error might be helpful to the monks in taking a stab at the root of the problem.
fat32 should be no issue, either, particularly since there are no ACLs with which to contend. Maybe there's something flaky with regards to the user under which Apache is running? Is there only one version of Apache on board? (I am noting from the other comment that there's only one install of perl).