1/ Run the following query to select rows from CM_CONFIGURATION_ITEM which contain characters outside of the standard English character set.
declare @str varchar(255)
declare @i int
set @str = ''
set @i = 32
while @i <= 127
set @str = @str + '|' + char(@i)
set @i = @i + 1
SELECT * from CM_CONFIGURATION_ITEM
WHERE ci_name LIKE '%[^' + @str + ']%' escape '|'
2/ Confirm that the rows located do contain either non-displayable or otherwise invalid characters.
3/ Backup table CM_CONFIGURATION_ITEM
4/ Run the same query as in 1/ but this time replacing the SELECT with DELETE to delete those rows.
5/ Once the delete has completed, restart the discovery_server probe.
6/ Check if you are now able to access the Trend and Group Trend reports for the groups/servers under which they previously failed.