Is he running a custom ROM?
(Some custom ROMS do have bugs, and may be the result of him installing the wrong version etc.)
No. Running stock
Overclocked?
(JRummy's overclock has been known on a few devices to cause some problems with the kernel and making SOME phones unstable, but it could also be the settings he set his overclock to.)
No. He does have Set CPU. But is underclocked.
Custom Boot Logo?
(Custom boot logo's have been reported to cause boot loops and or random reboots. I've personally never had the problem, but it HAS happened.)
No
Does he run a Task Killer?
(Android 2.0 + has a BUILT IN task killer, and he should refrain from using one! Same goes for Anti Virus software from the Market!)
No anti-Virus or task killers
Has he tried wiping Cache/Data Factory Reset?
(Sometimes all it takes is a fresh start, and may clear up some issues in his phone/sd card. Make sure he does it from CLOCKWORK RECOVERY!!)
No.
Last but not least, reinstalling the update/SBFing the SYSTEM ONLY SBF from TBH?
(Will reinstate the phone to an "Out of the Box" state.)
Would if he could but there is no SBF (that I know of) for the .340 update
EDIT - All these questions can be turned into a solution to his problem, just a matter of going down the list! (If non of these work then he may have a defective device.)