Actually, I've had this issue on all sites where I've used Seblod 3.x IF I enable both "Search Engine Friendly URLs" and "Use URL rewriting" in Joomla's global configuration (I'm using the standard Joomla-provided .htaccess and no SEF extensions). If I only enable "Search Engine Friendly URL's", all works fine.
I experimented with the different variations in Seblod > Options > Site > SEF but to no avail. So for now, I have settled for setting "Use URL rewriting" to "No", which means Joomla inserts the annoying "index.php" between the domain and the SEF extension (e.g. mydomain.com/index.php/users/user1 ... instead of mydomain.com/users/user1).
Like EclipseMedia, I'd appreciate any pointers re what I could check on. Thanks a ton, P