My normal response for this type of problem is to turn to Process Monitor, a free SysInternals utility from Microsoft. The problem is that it’s a pretty geeky tool, and requires a little patience and understanding to get useful results.
Of late, I’ve found myself firing up a completely different utility included in Windows 7 and 8 to monitor network activity. It’s a utility that quickly displays a lot of information about what’s going on. It actually can monitor several areas of your computer’s activity, but I’ll focus here on networking.