Enable and subscribe to the xml version of the report for troubleshooting purpose.
Use Internet Explorer and Notepad to view the xml report to look for invalid characters that may be cause the csv report to error.
Sample Error in xml report when viewed in Internet Explorer:
The XML page cannot be displayed
Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later.
An invalid character was found in text content. Error processing resource