[Update 11/6/08: I have found a solution to this problem. Apparently this issue happens to a number of folks with a pwn'd or not pwn'd iPhones. Sounds like a software glitch to me as many have said their phone worked until they upgraded. Some have had this problem in earlier 1.x firmware. Anyways, my solution is here.]
Continuing with my saga from yesterday of adding a custom firmware 2.1 from PWNAGE/QuickPWN, I discovered a little glitch today - my iPhone will no longer ring if it has been in standby mode or a long time. It is both annoying and frustrating because no matter what I do, I can't get rid of it (re-PAWNAGE and re-QuickPwn it both could not get rid of the problem).
I am leaning towards a software glitch because the problem isn't that the iPhone never rings. If the LCD is on, or if it is connected to a power source, no matter how long it has its LCD powered down, it will ring and alert me that it received a text message. However, by itself and if you let the LCD power down for more than 3 minutes, it felt like it entered some sort of 2nd stage sleep mode and when a call comes through, the phone baseband no longer has the ability to wake up the LCD and Ringer to inform me. The minute I press the power or home button during a missing call, it will lite up and start to ring.
I can't get a whole lot of information other than this link on this problem so I fear it can also be an one-off hardware issue. Would love to hear if you are having the same problem. BTW, if anyone is wondering if I have left the mute switch on, the answer is no. iPhone should be able to ring as is.
iPhone won't ring anymore
iPhone stopped ringing