Can't checkout for a customer, blank pages

I have one particular customer having trouble placing an order. They've received different errors which I couldn't duplicate & I believe are caused by her browser, so I took her order & am trying to enter it on my end by “Act on behalf of”. I've got all her items in the cart & when I go to either view the cart or checkout, it goes to a blank page. Sometimes when I click view cart it goes to a page showing only 1 product, but there are actually 301 items in her cart. I tried in Firefox & IE9 with same results.



Other customers are able to place orders successfully.

I seem to have corrected this myself by clearing the admin template cache.