My express invoice has wiped itself

[aarond]

I was using express invoice as I have for the last number of years and I was simply adding payments to invoices and when I got to my fifth payment I could see that there was something wrong. When I clicked payment I could see the customer wasn't showing up in it and I couldn't select any customers. Then I closed this window and went out to main menu and all my invoices had vanished.

 

No idea what happened and seeing as I was silly enough to only back up till October 2014 I'm missing quite a bit of information. Any ideas what could have happened and any way of fixing this?