Kim:
Check out IRS Pub 519, which can be downloaded from
www.irs.gov.
The five-year rule applies, but, IMHO, only from 12/8/2001 to 12/8/2006. It seems your employer is counting the 23 days in 2001 as an entire year, which is in error (again, IMHO).
I suggest you post this question to
www.thetaxguy.com, as he is the best available expert for taxes on foreign nationals.