iPhone crashing

I use my iPhone 3GS 32GB to play music, use Runkeeper with a heart rate monitor.

When I try to turn on the camera, the iPhone crashes?

Then I won't be able to use the iPhone for approximately the next 6 yours. I can reboot the iPhone, but it just crashes or sometimes works?

This is odd and is usually very reliable.

I have

Songs: 3,366

Videos: 5

Photos: 235

Applications: 155

Capacity: 28.3 GB

Available 451 MB

Version: 6.0 (10A403)

Carrier: irrelevant

Modem Firmware: 05.16.07

I just realised maybe it's a low memory issue, but not sure immediately how to fix this?

The diagnostics shows:

Incident Identifier: 0D6C8415-8ABB-40C4-BC0F-CDED7975B432

CrashReporter Key: 999c9dfeb9b6eac686da18c7ec22d4ead4aeb83e

Date: 2012-11-04 09:09:54 +1000

Reset count: 0

Boot failure count: 3

Boot faults: rst vdd_under

Boot stage: 80

Boot app: 0