Recently i moved a site in a new domain, i did it with a backup procedure used several times without big problems in the past. Also this time all is working fine in the new domain except the plugin installation. When i lunch the procedure for any new plugin wordpress point to the directories of the old site (having different structure). What i checked is wp-config and also option table but there it seems all configured well for the new domain.
Basically when i try to do an automatic installation of any plugin WP try to create the tmp file in the old domain directory. The others way of plugin installation work fine.
I really don't know where worpress found this old configuration.