If the sort order you want to use currently maps to "NULL", you must update the
mapping to identify the actual sort file in $SYBASE/charsets.
You can run select name, sortfile from syscharsets to see where the mappings are to NULL.
The workaround is...
sp_configure "allow_updates", 1
go
update syscharsets
set sortfile = "name_of_srt_file"
where name = "name_of_the_sort_order"