I tried the ini file which you copied to me, and changed nothing apart from the login details. On both of my systems it works as it should, so there's nothing remarkable about the configuration which would explain your issues.
If DSLstats isn't picking up the configuration when it starts, that rather suggests that the ini file hasn't been saved. Please check that you are closing down DSLstats properly before logging out or shutting down the computer.
I noticed in the ini file which you copied to me that you set the sampling period to 15 seconds. This is grasping at straws a bit, but it's just possible that this is too frequent for the rather old DG834GT. It would be better, for the time being, to leave the sampling period at 30 seconds to eliminate this as a factor.