[horde] Shared Calendar: only one group selectable

[Tom Gottschalk]

As Horde's admin user I created 3 groups:

1) "auth" (for authentication with IMP and my special-solution described in the 
PDF, see the link above)
2) "office" (containing members who work together and need a shared calendar)
3) "test" (empty)

Then I created a new calendar also called "office". When editing the calendar's 
permissions I only have one group to assign permissions to: "auth". The other 
ones are missing in the drop-down menu. I tested this with each calendar and 
everywhere's the same: only "auth" can be selected.

Why and how to solve this?

Maybe important: "auth" was the first group being created.