Submission downloads as Excel have unrepairable content

Recently (since about early May 2014), downloads of submissions generate an error message from Microsoft that says:

'Excel could not open Kippax-Daily-Takings(20q4-05-20 18_31_08).xlsx becaise some content is unreadable.  Do you want to open and repair this workbook?

If Excel cannot repair the file, some data may be lost.'

I have always been able to repair the file but something seems strange and this behaviour is unexpected and unwelcome.

We are truly sorry for the inconvenience you have been facing.

I've just cloned your "Kippax Daily Takings" form and examined with submission and downloading excell, I've found no problem.

But as I download your original form as excell format, I've found the same problem you are facing.

This error might happen when any of the form submitters submit the form with special characters which the MS Excell Spreadsheet is unable to read.

So, please make sure first going through your submission records whether it happened or not.

If you find anything like special characters in the submission record, delete those by editing that specific submission.

If the problem still persists, please let us know and we'll forward this issue to our developers to have it fixed.

Thank You.

Hi Bob
The form is only used to capture Daily Takings from a shop so it contain alphanumeric characters only. The only non alphanumeric one would be a $ sign, a colon or an equals sign which are hardly unusual for Excel.
I will examine the submissions and see if I can find something out of the ordinary.
Regards
Frank Owen
M: +61 416 108 242
Sent from my iPad
...

Hi Frank,

I tried to download your submission and opened it using Excel and for some reason it opened just fine. Which version of MS Excel are you using? have you tried the Open and Repair option of MS Excel? See image below:

I would also recommend to clear your browser's cache and try to re-download your submission and see if that helps.

Please let us know if you need further help.

Bryan

Thanks. Bryan
After repair, to works just fine but it's two extra steps.
I'm using Office for Mac 2011
I'll try clearing my cache
Regards
Frank Owen
M: +61 416 108 242
Sent from my iPad
...