Internet Sharing help

[SXRguyinMA]

Hi, I've got my computer hooked wirelessly through a USB adapter, and my wife's computer is hooked to mine through the LAN port via a crossover cable. I've got sharing enabled so she can use my internet connection. It's worked fine for a long time, but just recently it randomly disables the sharing on it's own.

She'll have no internet, so I go into the network and sharing center, and click on her wired network, and then properties, then the sharing tab, and check the "share this connection" box, and it's all good, until next time it randomly unchecks itself. Any idea?