Virtuemart blank page - urgent help needed

Hi,

Installed ECC+ (already working fine on 5 other sites) and checked the virtuemart options. The main Virtuemart page is still accessable but clicking on any category link results in blank page.
Deactivating, deactivating in phpmyadmin and finally uninstalling ECC+ did not help.
The problem is with the menu, when ECC+ was activ, all Virtuemart menu items pointed to VM registration page. After uninstall, the menu system still not working, we can not make any new menu items in virtuemart, only index.php?option=com_virtuemart exists and we can not edit any existing links either.
What happened with the menu system of Virtuemart.and how can we fix it without loosing any data?
PHP : 5.2.619
MySQL 5.0.51244
Thanks
George

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