The situation - At my girlfriend's parents' place there are six Windows 7 devices that are wired or wireless connected to a router: 3 dekstops and 3 laptops. There are also several smartphones using the router. The router is secured with WPA2 (AES).

The problem - We never had any problems with the router for over a year. But recently - about 3 weeks ago - my girlfriend's laptop (HP) and my laptop (ASUS) started to develop problems while trying to connect to the router. The router has stopped showing up from the network list. Sometimes it comes back and shows up, but then it keeps saying something along the lines of "Could not connect", and not long after that it dissapears again.

The range of the router is not the problem here, because we experience the same when we sit next to the router. Sometimes, if we are lucky, and waited a long time (10-15 minutes) without using the laptop for anything, the laptop will eventually succesful connect to the router.

The attempts - Of course, the Window 7 troubleshooter. We tried troubleshooting the connection problems and the wireless network adapter, but no luck. We also reset the router enough times to know that's not helping either. Here's the full list of things we tried, but did not help:

• Running the Windows 7 troubleshooter
• Resetting the router (more than once)
• Setting the router settings to factory defaults
• Disconnecting all other devices except one laptop
• Applying a system restore
• Trying static/dynamic IP/DNS - Dynamic is better, right?
• Enabling/disabling IPv6 - Should I keep IPv6 disabled?
• Running the command: netsh wlan stop hostednetwork
• Running the command: netsh wlan set hostednetwork mode=disallow
• Updating/reïnstalling wireless adapter drivers

The tests - To help finding the core of the problem, we tested the following:

• Plugging an ethernet cable in the router and in our laptops - worked fine
• Connecting someone else's laptop to the router (wireless) - worked fine
• Connecting our laptops to someone else's router - worked fine

The router - This information might be relevant:

• Router model: Sitecom 300N Wireless Router
• Router hardware: version 01

The DCHP Server's IPs range from 192.168.0.100 to 192.168.0.200. Router settings:

• Wireless channel: 12
• Channel bandwidth: 20/40 MHz
• Extension channel: 8
• Preamble type: Long
• 802.11g protection: Disabled
• UPnP: Enabled

The laptops - If you are wondering about our laptops:

• My laptop model: ASUS Pro64JQ
• Girlfriend's laptop: HP Pavillion G6
• OS: Both Windows 7 Professional x64 - with Service Pack 1
• My wireless adapter: Atheros AR9285
• AdHoc 11n: Enabled

The question - Does anyone have experienced the same problems as I do? Or does someone know how to solve this? Are there more tricks I can try, or settings I should change?

Note - Our laptops are not slow or old. My laptop is 1.5 years old, and the other laptop is just 5 months old. I know how to keep laptops clean and I'm pretty sure both laptops are not bloated with useless software.