Charge problem of Motolora Milestone

I found my Milestone can't charge intermittently, even after I sent to repair once.
Occasionally, I found I can charge after reboot. So that's the problem, as I installed an app to kill unknown programs running in background,  so shoud be due to I use it to kill some task that help to recognize "charge ".
The lesson learnt:
1. if you use <taskkiller> for android phone,  be carefully and don't kill some needed app.
2. If you use <taskkiller> and encounter charge issue, reboot the phone.