Mystery - need help starting Jetta

We are trying to find the problem of why our 1998 Jetta Wolfsberg will not start. We've replaced the battery and the starter with no luck.
What happens: We turn the key and get nothing - no sound of any kind. The dashboard lights light up and the radio turns on. After about 20 seconds the Jetta factory alarm will go off. We thought it was the starter and replaced it but same problem. We also replaced the battery. No luck. Any one have any ideas???

Sounds like either a fault in the starter circuit/igniton switch or starter inhibitor switch (Clutch depressed or car in park).