I've been running a daily report for a few weeks now and it has been working fine.  This week I suddenly began getting the error "...the file could be corrupted or unsafe...do you want to open it anyway."  I've tried all three formats and I get basically the same error in all of them.

I've tried recreating the report, but that didn't make a difference. 

I've attached a shot of the Excel error.

Is there a fix for this issue?