I've been having this same problem too, my phone will light up out of standby when a call in coming in, but the phone part doesn't show up till 5 seconds later, then ring once, then goes to voicemail. i've been missing a ton of calls because of this. Maybe its because I'm on AT&T? I turned off the dual mode to save battery life because I don't have a data plan on my phone, and the N900 doesn't support at&t's 3G bands, thus no need for 3G. But I'll try it nonetheless, and if that doesn't work I'll flash my phone. I'm just glad I'm not the only one having this problem