I'd start here;
http://www.irs.gov/govt/fslg/article/0,,id=110344,00.htmlA discussion of the differences between employees and independant contractors for the purposes of withholding income taxes.
I've seen this type of situation before where because of budgetary or other considerations, an organization will separate an employee and rehire them as a contractor. The Plan may consider to be the individuals status as a contractor to be a sham and thus no separation of service has occurred.
If this is, in fact, what happend, you've got other issues to deal with above and beyond the plan distribution.