Cache issue prevents emptying of shopping cart? - Joomla! Forum - community, help and support

hello,
i have site i'm publish. i'm having issue cache pretty sure preventing me emptying cart.

what happens add product(s) cart, when go checkout , view cart, if manually delete items in cart using red 'x' cart shows empty. but, when navigate other page shows cart still show have products in cart, though i've deleted them.

here testing site:
http://testing.neoclassics.org

here current site cache settings:
system cache - on-conservative caching/cache handler-file/cache time-30
server cache gzip page compression set 'yes'
plugin manager system cache - disabled

template - gantry cache 'on' 900 cache timeout
gantry gzipper - 'on' / cache timeout 600 / expires time 1400 / strip whitespace set 'on'

the shopping cart i'm using redshop, i've spoken them , has cache settings of site , not cart software. first time i've had problem.

any ideas? i'm not familiar cache , how manipulating it's settings can help/hurt site, although understand basics of having cache turned on along gzipper, etc.

actually think found in more simple fashion. cart module had , option "use cookies store content" , turned off.

it seems odd use function yet wouldn't overridden manually emptying cart...