XP Office 2003 problem with mail delivery

i am using WindowsXP pro and office 2003 pro. when i send an email to persons on the GAL (all internal contacts) some of the emails are not delivered. when i look at the properties for these recipients, i see the following in the display field: /o=SwerdlinCo/ou=SWERDLIN/cn=Recipients/cn=DSwerdlin, and on the email tab, there is no address listed. this is not the case with all of the recipients in the GAL, only a handful of them. i am the only one in the office using XP and 2003, everyone esle is using W2k and office 2k. they do not have the problem. if i put my user profile on a W2k machine running office 2k, the problem does not occur either. has anyone seen this problem before? i am trying to avoid uninstalling office from the machine and reinstalling it.