Cannot modify overlapping appointments due to the permissions settings.
Cause:
The 'Disallow overlapping appointments' check box is selected.
Solution:
Select the 'Tools' menu and select 'Set Access Permissions...'. Clear the 'Disallow overlapping appointments' check box.
1) Select the 'Tools' menu and select 'Set Access Permissions...'. (The Set Access Permissions dialog box appears.)
2) Select the 'Global' tab.
Set Access Permissions
3) Clear the 'Disallow overlapping appointments' check box.
4) Click 'OK'.