Group objects quit working w/o owner

The land is set to group owned...but whenever the owner of particular objects logs out, the objects stop working. What's up???

Thanks

See if those items are really set to the land group (doesn't need to be deeded, just set, and double-check this because sometimes the viewer will display in the last group it saw for items that aren't really set). It's weird that they will run when not set to group but the owner is present, but I've seen that before.