[TYPO3-shop] blank eshop pages after upgrade PHP 5.2.0 to 5.2.1

[dana.novotna at ekodomov.cz]

When I enable "displayErrors"  in Typo config, I get the error mesage on 
e-shop page:
 
Catchable fatal error: Object of class tx_ttproducts_product  could not 
be converted to string in
/www/hosting/ekodomov.cz/www/typo3conf 
/ext/tt_products/model/class.tx_ttproducts_product.php
on line 69

I am still lost.

Unfortunately, we have decided to downgrade php temporarily because 
e-shop must go on... and we will try to investigate on another server 
using dummy pages...

Thanks
Dana