WDT timeout, unsolvable?

Hello,

A few months ago, my iPhone 3GS started rebooting every 5-10 minutes, only when the mobile network was activated.

I did a hard reset, and everything was fine again.

But now, there're problems again... Now, the iPhone resets 3-5 times a day, but also when airplane mode is activated.

When you look at the crashlogs, it's always because a "WDT timeout". There's one other topic about this subject (https://discussions.apple.com/thread/3500622?start=0&tstart=0), I tried every possible solution, but it didn't help.

I didn't try a hard reset (yet), because I don't think it's convenient to do this every few months or so.

My questions are:

1- What's the WDT-process?

2- Anybody has a solution for

(the Apple helpdesk didn't seem keen to help me)

Thanks in advance!

Kind regards,

Joris