oh, sorry... should have been more specific
site cloning has been ruled out as source of the problem
WPML support is claiming this is an issue between their plugin and Domain Mapping plugin
this is the full code that supposedly would correct the issue, but i am not much willing to try without knowing what it does...
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
#RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1
[edit: my installation is SubDomain, there are a pair of lines from SubFolder]