Small details make a big difference
Today I saw two clients who described their situation the same. They each had broadband Internet and could get online with one computer that was wired to the network but not with a wireless.
When I got to each of these locations they were each connected to the wireless network but weren't getting any Internet. The first client was connected to the wrong network, an ad hoc connection to an HP device somewhere.
The second client was much more complicated. Like the first they were able to connect to the wireless network (even the correct wireless network) but not the Internet. It turns out that was just the beginning. They also had a printer that would print just fine from anywhere except from a remote Quickbooks terminal (too geek to explain). They were also trying to setup an new network based time clock.