Hi,

And thanks for the reply.

The two files are both pre-existing. They exist as "empty" templates in another folder with just the column headers - these are copied into th eoutput folder and then these are the spreadsheets used to output to. I've used this method many times on .xlsx spreadsheets withotu any problems at all, and as I say, the package works fine when run from Visual Studio.

I've also tried using all combinations of 'Delay Validation' and 'Validate External Metadata', but the problem still persists.

I'm now wondering if there is a specific driver/provider for .xlsb spreadsheets that may be missing from the server. Anyone any ideas how I find this out?

Regards