I had configured a 1801 and 1750 series router with a line aux 0 for dial-up backup with a speed of 115200, but every time I type the show running config command these line changes to whatever value.
This could be an indication that your router and modem aren't talking to one another. I suspect that the dial backup isn't working like you want it to.
Physical connectivity, aux port config, modem dip switch settings, modem cap, etc.