Thanks Ryan, I got rid of the errors by commenting out the line mentioned in the errors... then a second error popped out:

recoverable fatal error: Object of class stdClass could not be converted to string in /home/XXXXX/sites/all/modules/ubercart/uc_product/uc_product.module on line 232.

Commenting also that line out seems to be a temporary error less solution. I tried to double check the modules and settings, but did not see anything strange in permissions etc... (in case Ryan it helps you, please don't hesitate to PM me for log-in to take a look)