Dave
I had serious problems also,firstly it appeared that the correct size file was downloaded into the data file, but on opening up the programme, the file reverted back to the original file (size waise and records etc)
everything I tried was to no-avail until i did a complete re-install of the software - it then worked fine.Might be worth a try?
Out of interest, how old is your pc? Mine was having other performance issues, mainly running very slow over the past few months,so it may be something outside the parametes of the software?
HTH
Rich