Just a note for others searching this topic - we just had the same behaviour on SQL Server 2014.  Bouncing the SQL Server Agent service resolved the problem.

Obviously...

Further, one way suggested is to use a Terminal Server to deliver the reports. Therefore the TS does the rendering. Its a bit clunky but I guess thats...

Thanks for your reply. I think this is something the MS have overlooked, I cant help think they are forever playing catchup.

Craig.

You would think that two MS products would work seamlessly together. Does anyone know whether SQL2010 handles Excel any better?

Thanks for your reply - I suspected as much.