Duplicate attendee in TO line of Meeting notice??

[KES]

I send a meeting notice as usual:

i.e. TO: ... Smith, John; Jones, Roger

After a user accepts a meeting notice, and I go back to look at the
meeting notice and his address now appears in the TO line in two
different formats. The first being the expected format, the underlined
Display Name and the second is listed in the meeting notice by the SMTP
address.

i.e. TO: ... Smith, John; Jones, Roger; Roger Jones
<[email protected]>

Anyone know what would cause this??

Thank you!
KES