please check
a several sequences in admin_articles_all.php file like this:
 
$sql.= " INNER JOIN va_articles_categories ac ON .....
 
must have ".$table_prefix." - not "va_" prefix
 
$sql.= " INNER JOIN ".$table_prefix."_articles_categories ac ON .....
 
it's generate error if tables prefix does not "va_"
 

also in block_order_info.php

Yes there could be a problem if you want to use a custom prefix for standard ViArt tables and below is the fix:
http://www.viart.com/downloads/va_prefix-4.1.zip
 
We didn't include files for custom forms because they are not in use right now.
 
Regards,
ViArt Team