"[I]f a qualified plan's records are not reasonably available to segregate an employee's pre-'89 401(k) amounts from other amounts that, as of the '89 date, were credited to the employee's account, then, for purposes of determining what is an eligible rollover distribution, the plan must treat the other amounts as ... pre-'89 401(k) amounts ... [which are] ineligible for rollover when distributed on account of hardship."  MORE >>