Sounds like some driver issues. Download the latest network drivers for you NIC. Then uninstall the Wireless NIC drivers and install the latest. Hardware wise, it sound as if it works since it is working.
Another possibility, sort of an unlikely one, is if this is the same laptop that you use at work then it is possible that there are settings or 3rd-party applications installed to prevent you from connecting to WiFi network. This would be due to company IT policies. If this is the case, then it is likely that it would only effect Windows 7 because it is rare to allow a personal Linux laptop on a corporate Windows domain network.
Please don't assume it is the latter reason unless know for sure. I don't want you accusing your IT department at your work for something that doesn't apply to your system or company's policies.