I have upgraded to shopp 1.2.3, and have noticed this error repeatedly in my error log:
Shopp: The shopp('cart') tag cannot be used in this context because the object responsible for handling it doesn't exist. [shopp-cache-helper.php, line 153]
I'm also getting this error:
PHP NOTICE: unserialize() [function.unserialize]: Error at offset 40 of 41 bytes [DB.php, line 845]
This is happening even though there is nothing in the cart.