Have you ever tried running gracia on that computer before?
Few suggestions: -Check other servers (on clean client ofc)
-Close any not-needed programs
-Get rid of viruses, spywares etc.
-Software upgrade
-Maybe hardware (check this site http://www.lineage2.com/pds/pds_client.html)
Maybe I forgot few things but there is something slowing down your computer to load those textures or some files are simply missing, somehow.
PS: Post your Critical Error message