[TYPO3-Solr] Initialize Index Queue Error

[raka]

Hi all,

I'm using version 2.1.0.

On "Initialize Index Queue" I get the following error:

     Core: Exception handler (WEB): Uncaught TYPO3 Exception: #1309272922:
         The page for the given page ID '' is not marked as root page 
and can therefore not be used as site root page. |
         InvalidArgumentException thrown in file 
/.../typo3conf/ext/solr/classes/class.tx_solr_site.php in line 65"


Root page is set but it seems that $rootPageId in class.tx_solr_site.php 
is empty.

Any hints?

Thanks in advance
Raffael