#1. Most of the time the styles will do that during a move and need to be rebuilt. Will get that fixed for v8.
#2. That is one query where we are using a subselect. So, what's probably happened is your new server is running an older version of MySQL.
For now what you can do, if the group is empty, is just manually delete it with this SQL query (changing the # to the actual group number):
update ubbt_GROUPS
set GROUP_IS_DISABLED='1'
where GROUP_ID='#'
