Scheduled Report Excel 2007 Email Attachment Corrupt

On BI Server CE 5.0.1 I have published a report and I can run the report and get Excel 2007 output. I then created a schedule for the report, also with Excel 2007 as the output, and added an email address to receive a copy of the report. When I execute the schedule, I receive the email with the attachment (it has the correct .xlsx extension), but the file is corrupt - it is being truncated. The .xlsx file only contains a few hundred bytes, in a hex editor I see a reference to docProps/core.xml and then the file ends. If I go to the console and look in the output folder for the scheduled report, the report is there and it opens normally, so it is only the email attachment that is a problem. If I change the output type to Excel (.xls) then it works fine, I get the email and the attachment is not truncated so it opens normally.

Am I doing something wrong or is this a bug, if it is a bug, is there a fix?

Thanks
Sean