The product continues to work with 4.1.8 (please see:
http://www.vbulletin.it/).
The only reason why banners disappear may have their reason because:
1. You reverted the templates where you had banner replacements or you have upgraded your styles.
2. Templates or ad locations have disappeared.
3. You have disabled all plugins from config.php (DISABLEHOOK) and/or the options and forgot to reenable them.
4. You have deleted all files before upgrading, instead of overwriting existing files with your FTP client. This practice ensures you have fresh files, but will break all products which have additional files.
In all these cases there is nothing I can do about it