Well...... downloaded a new copy of the touch screen software onto a different PC running XP ....... and it uploaded with no errors first time.

Now the "old" PC runs 98SE and the touch screen set up folder has quite a few data files associated with it ...... not that they should influence to application software at all.

So, a little inconclusive other than it appears to be a PC problem ..... could be the serial port I suppose, as the PC is otherwise seemingly OK.