Able to detect but not connect to network

"Some possibilities to check;

Your router has no IP addresses left to assign.
Log on to the admin interface (as per skypecakes's answer) and increase the range of addresses.
None of your wireless devices support the channel the wireless is broadcasting on.
Change the channel to a more common one (say, 6).
Router has gremlins.
Reset router to scare off gremlins."

"Just a note on picking channels in areas that have other 802.11 networks setup. If you are using b/g you will see best results by choosing a channel that is not in heavy use in your environment. Use a utility such as inssider to find this information out. Once this is determine pick either channel 1, 6, or 11. Checkout the Wikipedia entry on 802.11 for the reasoning of why those particular channels. The particular information from the Wiki entry is below.

Besides specifying the centre
frequency of each channel, 802.11 also
specifies (in Clause 17) a spectral
mask defining the permitted
distribution of power across each
channel. The mask requires that the
signal be attenuated by at least 30 dB
from its peak energy at ±11 MHz from
the centre frequency, the sense in
which channels are effectively 22 MHz
wide. One consequence is that stations
can only use every fourth or fifth
channel without overlap, typically 1,
6 and 11 in the Americas."