Not sure but first
Open Nework Monitor click Help on the menu bar and choose check for updates. You should be using Version 3.4
Then click Capture Settings and make sure that your wirelss adapter is checked.
Then make sure that your wireless adapter is actually working and that your wired connections is not handling all traffic
into the search or run dialog box and hit enter
from the menu bar select advance and then advanced settings (if menu bar is not present hit the "Alt" key to expose it.
In the top frame titled "Connections" select your wireless adapter and then use the green up arrow to the right to move it to the top so it becomes the priority adapter when present.
See if that helps and keep us posted.
Also after starting and stopping a capture expand any traffic reference in the left pane referencing "System" and see if the IP address of the wireless card is listed
Been having a problem similar to this. I have Microsoft Network Monitor 3.4 and it doesn't show either of my ethernets in capture settings while it shows virtual Microsoft ISATAP adapters. Both ethernets (Marvell Yukon 88E8056 PCI-E on an asus rampage extreme II ) are properly installed and properly appear in registry and everywhere else :S