Unable to run reports without error

Unable to run reports without error

Of recent, when trying to run a report and not customizing anything other than selecting Current Month, I receive "Unable to Process Your Request".  I've logged out, back in, and using the standard report, Tickets by Account and again, only changing the date range to Current Month.  I am an Admin to this account and have successfully run various reports in the most recent past w/o issue.  All other functionality outside of Reports works w/o issue. 

Thank you for your thoughts and help as to why this is occurring and, how this can hopefully be resolved.

Sandy