CAn't set the clock on Navigon 2000s GPS

Caution! Selecting the (Cancel) button during these steps will cause the
NAVIGON device to cease operation and will require the user to reset the device.

First Time Startup
When you first start your device, the LANGUAGE SELECTION WINDOW displays.
1. Select the appropriate language and tap OK.
The DISTANCE UNIT SELECTION WINDOW displays.
2. Select either Kilometers or Miles and tap OK.
The CLOCK SETTING WINDOW displays.
3. Select either 12h (am/pm) or 24h and tap OK.
The selected options will be used by the device.

did you try reset to get back to the first time setup as posted above?