secure network shows up unsecured?

I am running a standard cable internet connection (Time Warner in NYC), using a D-Link DI-524 wireless router (802.11g, 2.4ghz). I have two machines, one is a MacBook with built in wireless adapter, the other is a Dell PC with a Linksys Compact Wireless-G USB adapter.

For a few months, things were fine. Lately, a few strange things are happening. First, both machines (but more so the Dell) seem to have trouble connecting to the preferred, secure network set up in my apartment...and instead opt for the unsecure network belonging to someone else in the building.

But even stranger, right now my private network is showing up as *unsecured* even though I haven't changed any settings.

I've of course rebooted, also hit the reset button the router, powered down both the router and the cable modem. Any idea what is happening here?

Thanks.

Practical Wi-Fi security overview

Wi-Fi is an abbreviation for wireless fidelity and is used to refer generically to any type of wireless network based on the IEEE 802.11 standard -- be that network 802.11b (an 11 Mbps technology, currently the most popular form of Wi-Fi), 802.11a (a 54 Mbps technology, a newer and emerging favorite), 802.11g (55 Mbps), or other formats.
An industry consortium known as the Wi-Fi Alliance, composed of leading wireless and equipment vendors whose mission is to certify 802.11 products for interoperability, makes sure that all equipment described as Wi-Fi can work together. This group seeks to create a global brand and identity for 802.11-based wireless LAN (local area network) products. All 802.11a, b, and g products can be called Wi-Fi, but only products that pass Wi-Fi alliance testing can label their products as "Wi-Fi Certified" (a registered trademark).
Wi-Fi offers users easy wireless network set-up, access, and use. But because the standard was designed with only limited security capabilities -- basically, to foil casual eavesdropping rather than more powerful forms of attack -- it's essential for managers and IT professionals alike to understand that Wi-Fi is subject to well-known and well-documented security vulnerabilities and weaknesses.
This IT guide covers basic Wi-Fi concepts and terminology and discusses how important security issues are for proper deployment and use of this powerful and flexible networking technology. The sections of this guide include:


>> Wifi pune, Wi-fi Pune, Pune Unwire - The realities of wireless security

>> Wifi pune, Wi-fi Pune, Pune Unwire - Wireless security options and add-ons

>> Wifi pune, Wi-fi Pune, Pune Unwire - Finding the right security model

>> Wifi pune, Wi-fi Pune, Pune Unwire - Planning for the future


Thanks