There is an issue at present with some attached Excel and Word files throwing an error when downloaded and opened. You will likely be getting an error like one of these:
If you select "okay" it will take you to this:
In Excel it will probably look like this:
Clicking on "Yes" or "Open and Repair" will recover the file. We have not found any instances of data actually being lost.
We are working on repairing this - sorry for any inconvenience in the meantime.
1:20pm 29 May 2015 - Issue resolved.