Ecart Store Details in Database issue...

Hi There
I've been successfully using the 'Store Cart Details in Database' feature for a couple of years now and it's always worked well.

But now I seem to be having a problem with one of my customers who is saving their cart (to retrieve at a later date) but when they return it hasn't saved their order.

Everyone else seems to be using the feature just fine. I'm now thinking the issue with this particular customer is he's trying to save extremely large shopping carts 600+ items, as when I got him to do a test and only save 2 items it saved just fine! But then when he tried to add a large order again it didn't save and actually deleted the older (2 item test).

Is there a size restriction on saving carts to a database or can anyone think of any other reasons why saving very large carts would make it not save and then their past save in the database disaspear?

I'm using Ecart 4.5.2 in Dreamweaver CS5 and the database is a basic online phpMyAdmin database.

Many Thanks