If this is only happening for some of your favorites, then a possible reason is that the favorites were created with leading zeros (007 or 07 as opposed to 7). This will be fixed in a future version but for now the solution is to create a new favorite without any leading zeros.
If this is happening to all channels or channels that do not have any leading zeros in them then please see this FAQ for another possible solution. It is also possible that you have designated a specific receiver to use for the Mini-Guide source but that receiver is no longer available. If this is the case, you can try changing the Mini-Guide Source option back to the default (current receiver).