The old problem, solved originally for Plesk 9 (http://codex.wordpress.org/Configuring_Wildcard_Subdomains_for_multi_site_under_Plesk_Control_Panel) is back again.
Aftter adding vhosts.conf with wildcard in subdomain is to website's folder redirected even subdomain "webmail", which is dedicated to webmail on server (and which have been working fine before adding vhosts.conf).
Solution for Plesk 9 (linked above) is in renaming files zz001_atmail_vhost.conf & zz001_horde_vhost.conf. But they're removed from Plesk 10…
Any help will be really appreciated...!