There is a very simple solution to this problem. You just need to add the grid in question to the list of grids under Preferences/Opensim. This might happen again with other grids; once more, simply a...
.NET8 is toast in november. dev meetings are every tuesday 11am open to all http://opensimulator.org/wiki/Office_hours
AFAIK there's is some issue with libgdiplus from mono that needs to be dealt with