This happens about once a week, I'll get a text message but notice the led isn't blinking. Then I look closer and it is so feint it's almost off.

I don't remember this happening before installing the LED Notifications app about 6 months ago. Is it a bug in that does anyone know?

FYI a reboot fixes the problem, so it's not a biggie, just annoying.

Or maybe I should shout "OMG! The LED doesn't work from time to time! I'm smashing this N900 to bits and buying an iPhone or Android phone!!!"

... or maybe not. My N900 is like my daemon as in The Golden Compass

Restarting MCE will also fix this.

`kilalll mce` as root.

I had this problem in the past but since I followed this: http://talk.maemo.org/showthread.php?t=64191
I don't have this problem anymore, I'm almost sure that it is related:
This mod will make mce no longer use the light sensor for calibrating screen brightness (I and many other found that annoying) but it also deactivate the notification leds calibration, the leds are now very bright in the dark.
I think that the feint led is caused by mce which think that the N900 is in the total darkness which in fact is in your pocket, so it will feint your leds and make them invisible when you take your N900 out of your pocket.

Thanks for the help, I'm checking out that thread now.