If you're using BVCommerce 2004, we may know the issue.

We had one incident where the owner of the website went to checkout and each time they did, the page would crash when they went to the shopping cart.

After further investigation, here's what we found. They had items in their cart already. When they went to checkout, it was trying to read those items in the cart. This is when it crashed. It turns out that they had just changed the pricing of one of the products that was in the shopping cart. So, we are finding that because it changed, it was causing the shopping cart page to crash.

How to fix it... We went into the admin settings tab. Went to the orders section. We changed the number of days for the items to stay in the cart from 2 to 0. Then, we ran the shopping cart cleanup. This reset their cached cart. Then we reset the number of days to hold shopping carts to 1 day. And, we make sure the cart cleanup runs every day. We figured this would eliminate any problems with items being in the cart when sales or promotions ended.

Here's an example. If I put a sale item in my cart on Friday, I may want to finish up the order on Saturday. But, if the sale ended Friday, it would cause a crash. The solution described above fixed the issue.