[TYPO3-english] tt_address is not working at all

[luca]

Hi,

I have installed tt_address in my t3 site.
Altough  was able to create a tt_address group in my storage folder I 
cannot use the extension at all...
If I insert a record (in any page), or I try to access a page in which 
I've previously tried to insert an address record, it shows the 
following error...

=====================================================================================
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result 
resource in /var/www/vhosts/xxxxxxx.it/httpdocs/t3lib/class.t3lib_db.php 
on line 795

Warning: Cannot modify header information - headers already sent by 
(output started at 
/var/www/vhosts/xxxxxxx.it/httpdocs/t3lib/class.t3lib_db.php:795) in 
/var/www/vhosts/xxxxxxx.it/httpdocs/typo3/template.php on line 632
=====================================================================================

Do you have any idea how to solve it?

My config is
TYPO3 CMS ver. 4.2.1
tt_address 2.2.1

thank you

Luca