I've got a VERY odd problem. I'm getting the error "Word was unable to open the data source" in Word 2007 whilst trying to perform a mailmerge.
I have tried using CSV, TXT and XLSX files as the datasource. The process works the first time after the data files are created but then seem to corrupt in some way and won't run again.
The whole merge runs fine on other computers - and even on a virtualised copy of the computer that isn't working!