This is most likely the result of someone you know that has our email address in their outlook express address book, and they are infected with the WORM_KLEZ.H Virus.
You will notice that the emails are pretty obviously forged by the virus and you can find out by checking the header information for the orignating IP like you eluded to. Send us the complete header information and ALSO check it out via a ARIN whois, also educate yourself about this virus and how it works more info here:
http://www.antivirus.com/vinfo/virusencyclo/default5.asp?VName=WORM_KLEZ.H