MS Office - Word doesn't read the merge data file

Question

major problem this, i already lost several days of work time and i just can't find a solution. We have Word documents with merge fields in, the docx files are connected to files that contain the data, these files are tab-delimited textfiles. In my code i get a error when i try to execute MailMerge.OpenDatasource(<pathtofile+filename> but that seems logical as i also get the same 'cannot open the datasource' error in Word directly, at least on that machine.

So far i have tried on 3 other Windows machines, each having the same Word version, 2501, and on all 3 when i open the word document Word asks me to browse for the datasource file and then the data is loaded.

But the development machine just refuses to load it, these are the same identical files, no differences, even saved in the same path, same Office version, when i browse for the data file it keeps saying it doesn't find it, although it is present in that location.

Interesting enough when i empty the file and do the same Word tells me there is no data in the file! Different error which proves it does find it.

Does this ring a bell for anyone? Word does not prompt me to ask for the formatting (windows default) on that machine, it does on the other pc's.