Overtime for exempt and repayment of overpayment

I worked for a company as an exempt employee. My title was Technology Architect. I worked a lot of overtime - which did not bother me all that much at the time. From the week of April 2 (1999) to the week of November 28 (1999), I worked a total of 453.5 hours of overtime of a normal 40 hour work week - or 204.5 if the normal week was 50 hours. I actually continued work until May 2000 but do not have my time sheets after November.

Consequently, the company direct deposited paychecks for June and July 2000, which they are wanting back. The June 2000 amount should have been for my remaining 3 weeks of vacation along with floating holidays, management days, etc. They are claiming that the proper paperwork was not filed on my behalf to entitle me to receive any of those days and will not complete the required paperwork for me. This whole thing irks me since I worked so long and hard for the company and this is how they repay me.

Do I have to pay them back for the monies they mistakenly deposited? If so, how do I go about getting my vacation, etc. paid for? Do I have rights to any overtime pay?