Help with blank screen problems

[myth3_16]

Hello everyone.

I tried upgrading my zen install from 1.3.9f to 1.3.9h but something went wrong and i lost all my new customers from the admin screen (the dates were there but the names weren't).

So i deceided that I'd tried to do a roll back by putting the whole of 1.3.9g onto my server. This has helped but now I can't EDIT any orders.

When I click on orders in my admin and click on edit it comes up with a blank screen. Any ideas on what might be causing this?

It worked in 1.3.9f.

Any help would be appriciated.

Kindest Regards,