[TYPO3-commerce] Categories and backend errors

[Martin Keller]

T3 4.2, commerce 0.9.6 and graytree 0.2.0, PHP 5.2.0

I am not able to create categories.
First, I click on "Commerce/Category", then there is the following 
error-msg in the 3rd frame

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL 
result resource in /home/bin/typo3_src-4.2.0/t3lib/class.t3lib_db.php on 
line 808

If I then click on "Category/New Subcategory" in Treeview frame, I get:

Not Found
The requested URL /typo3conf/ext/graytree/mod_cmd/index.php was not 
found on this server.

The extension states, it is missing this file too..

Any idear?