Strange problem detecting wireless network

Hello friends, I have a very strange problem with my laptop and the wireless network.
The problem is basically that the network sometimes appears in the list of available networks and sometimes not. I have to refresh the list several times to detect the network.
When the network is detected I can connect to it and everything works fine inclusive Internet, so I think the problem is only to detect the wireless network. Very strange.
I tried changing the configuration of the network adapter and the router without any success.
I am using Windows Vista Home Premium x64.

This is the configuration on the wireless router:
Band: 2.4 GHz (G)
Mode: AP
Auth type: Open system (Security WPA-TKIP)
SSID: Enable
Channel number: 3
Send rate: 54M
Radio power(mW): 100%

And this is the configuration of the network adapter (Intel WiFi Link 5100 agn, with drivers updated):
802.11n Channel Width (2.4 GHz): Auto
802.11n Channel Width (5.2 GHz): Auto
802.11n Mode: Disabled
Ad Hoc Channel: 11
Ad Hoc Mode: 802.11 b/g
Ad Hoc Power Management: Disabled
Ad Hoc QoS Mode: WMM Enabled
Fat Channel Intolerant: Diabled
Mixed mode protection: CTS-to-self
Power Management: Highest
Roaming Aggressiveness: Medium
Throughput Enhancement: Enabled
Transmit Power: Highest
Wireless Mode: 802.11b/g

I hope you can help me. Thanks for the answers!

Is there a particular reason why you selected channel 3 on your wireless router? Try using either 1, 6 or 11 as those are the primary channels.

Thanks for the answer. I tried using all channel numbers (1-10) and the auto option on the router, but the problem persists.