[TYPO3] company_database: problems with display and categories - 2nd attempt

[Gunda]

I installed the extension cl_company_database

I have got a page for the company list, one for single view and a sysfolder to the 
records (which is referred to as starting point). I used the example template delivered 
with the extension and added the company database template as static template in 
the root setup. 
This is installed on Typo3 4.0, Windows XP MySql 1.4, latest static info tables 
installed

This is what happened:
Error messages:
warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result 
resource in c:\typo3\htdocs\typo3wamp\t3lib\class.t3lib_db.php on line 801
warning: cannot modify header information - headers already sent by (output started 
at c:\typo3\htdocs\typo3wamp\t3lib\class.t3lib_db.php:801) in 
c:typo3\typo3wamp\typo3\\szsext\cms\tslib\class.tslib_fe.php on line 2767

Results:
(1) I can only see the records in the sysfolder when I select the list module
(2) The two words "company" and "city" appear on the frontend, nothing else
(3) I cannot select the categorie for single items added
(4) the categories appear listed in the plug-in configuration (which I selected for 
display) but the single items do not (the list boxes are empty), although I added 
single items.

I have checked everything I can think off, installed it twice now and searched the manual. Can anyone help 
me please?