T43 on original battery stopped charging and now on new batt.

My mum's T43 was working great on it's original battery (about 1:30 on normal everyday tasks, full brightness, full WLAN power, etc). I set it up to only charge when it gets below 10% to keep it's capacity and avoid the all too common "topping up" charging rather than fully discharging and fully charging to 95%. Suddenly one day it got to about 8% apparently, and my mum plugged it in and it never charged, at all. Battery was still detected, everything looked normal except it just wasn't charging. It must have been drawing power from the adapter alone, since there was no current flow (at all) from the battery. Tried plugging in and so on 10's of times, cleaned the contacts at both male and female sides of the DC side.

Then, it started crashing a few seconds after logging in only when the battery was installed. I reinstalled Windows 7, i assumed it was a critical standard DLL or something that got corrupted. After that, it didn't crash with the battery in, still wasn't charging though. Got a new battery from eBay (yes it's OEM) and still isn't charging at all.

Can someone list to me (simply) the main components of the charging system and what the culprits could be here? Should i go and order an OEM charger off eBay for her? I told her i'm sure it's the charger. Could it be corrosion between the battery terminals and the computer circuitry?