I find that 90%+ of all failed/problematic enterprise activations can be solved with three steps:
1. Hard reset the handheld (read: pull battery)
2. Set a *NEW* activation password (new meaning don't try re-entering the one you just assigned/generated - I'd recommend manually setting the PW rather than generating+emailing.)
3. Patience... Especially around 90% when it's dumping the users 2500 contacts into the device OTA! I recommend placing the device screen down and walking away for 15 minutes.