Version:            (using KDE KDE 3.5.8)
Installed from:    SuSE RPMs

The case:

Got korganizer invitation from other user (myself at work) via mail. The KDE version at work is exactly the same as the one at home.

Accepted invitation from within mail part (kmail), the entry was added to the calendar and kontact summary view.

The day of the invitation was changed, an update mail was sent out.

I accepted the change from within the mail part of kontact. The calendar entry was changed, but the summarty view suddenly contained both entries, the one at the original day and the one at the new day. Switching between the different parts of kontact didn't fix the problem.

Quitting kontact and starting it again fixed the problem, only the entry at the new day remained.