When connected via wireless, laptop can't see other machines on lan

[#1]

When connected to our MI424-WR Rev C router via wireless, my laptop can connect to the internet, but it can't access shares on other machines connected to our lan by ethernet, nor can its shares be accessed from other machines.  When connected via ethernet, however, everyone can see everyone else just fine.  This wasn't always the case, as it was working fine through either type of connection just a few weeks ago.  The only changes that have been made are Windows updates.  All of the machines in question are running Windows 7 Home Premium.  The router firmware is version 4.0.16.1.56.0.10.12.3.

Note: the machines can ping each other just fine, no matter how connected.

[#2]

What do you see in network and sharing center?

What kind of network does it say you have and what appears if you run network discovery?