Rewrite rules stopped working after upgade

[manos]

Ok here we go....
I' m using Plesk 7.5.4 on a dedicated fc2 machine.
In the past I had to move all my clients (subdomains) from a crappy server to my current location.
Most of my clients had programed their pages and links in the format www.myclient.mydomain.com.
I Know that this is WRONG (I didn' t design the sites) but the old server never complained and everything worked OK. When I moved my clients to my current Plesk server the links stooped working so I had to come up with a solution. I could not rewrite all the html code and my clients had allready printed cards with the format www.myclient.mydomain.com.
So I placed a .htaccess file on each subdomain like this...

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.myclient.mydomain.com
RewriteRule (.*) http://myclient.mydomain.com/$1 [R=301,L]

and then I added for each client a CNAME DNS entry like this...

*.myclient.mydomain.com --> myclient.mydomain.com

Everything worked fine until a week ago when I updated Plesk to the latest 7.5.4 components.
Now the rewrite rules don't work any more.
ANY IDEAS???
TIA