From Samsung's website regarding your TV (in the fine print at the bottom of the main product page):
"To use Samsung’s Internet@TV and AllShare features, a Samsung Wireless LAN Adaptor (RRP $79) is required. Click here to learn more. "
When you click there, you go to the page for their WIS09ABGN adapter and it says there:
"By connecting your wireless LAN adapter into the TV, you can instantly access many of your TV’s key features such as Internet@TV, AllShare and Samsung’s Touch Remote Control. In addition to the features, you’ll also be able to enjoy content from your compatible multimedia devices (PCs, cameras, Blu-ray disc players, mobile phones) without the hassle of messy cables or wires. * In order to use internet@TV and AllShare feature, your TV must be connected to wireless IP sharer."
Sounds to me this is saying that AllShare feature is only available when you plug in their optional wireless dongle. Something about the presence of their adapter must activate the feature in the set. That makes no sense to me if you say there is already a direct LAN connection on the set and you've connected to it already, but that's not unheard of.
I see various comments in a Google search saying that you must also download and install Samsung's PC Media Manager to get ALLshare to work.