I have a problem where sometimes all of my notification sounds stop working, even vibrate doesn't work. I reboot the phone, only thing I've found to fix the problem. Sometimes I have to reboot after an hour, sometimes a week.

 

wow these problems are curious.
it would help for everyone to include their
rom/kernel. I use dgalert for sms notify.
I moved all apps to /system/app
I use stock overclocked w/picasticks kernel and
my phone boots and is ready to go in 30 sec.
I have no issues whatsoever.
Installed & removed busy box/ rom manager(fix permisions)
also copied su to sbin so root checker says everything
is spiffy
I noticd Xiona whatvr kernel shows compatability
issues on stock roms prolly others too when I tested it.
I see no reason for any Roms I just put Go launcher EX
and removed the dafult launcher apk.
I like not being linked to a google acct. I downlod apk's online

 

I have had a similar problem. I keep all volumes to the highest lever using Quick Settings. At night I turn down the Notifications volume as I am a light sleeper and don't want to be awakened for a text but do for a phone call. After waking, I turn the Notifications volume back up to max using Quick Settings again. From that point on I get no notifications of texts either via sound or vibration. I have to turn the phone off and back on to receive them. Just figured it is one of several bugs in the phone.

 

I learned from another forum that when my vibrate stopped working on my LG optimus- only for SMS and email that you can kick start it into working by downloading Vibrate Tools from the market. I set the vibrate as the sms pattern in the vibrate tools and it all worked again. Then I deleted vibrate tools and it works fine. (although I re downloaded it so I could have it in case it stops working again!)
Whenever my tone stops working for SMS I have to reboot then its fine....

P.S. m-cman... Download Quite Sleep Free if you want to silence everything at night- it allows for a white list of people who can get through the 'silence'.