Same problem here. Been looking online for people's suggestions and trying them with no luck.
I mean if everyone is getting this error, then it can't be a server issue. We are not all hosting on the same server.
This is actually putting me off, and I'm now considering a different shopping cart solution. researching now for an alternative.
All these errors, precautions you need to take before you update, and it keeps failing is very frustrating.
I've spent time and money on modules, theme etc, and can't run a simple update? I hope they fix it soon, but from what I can see these problems are not going away. People have had them for ages. I cannot believe they do not mention how buggy a system is, in reviews.