wheel - 6:58 pm on Oct 30, 2012 (gmt 0)
If I had to guess, you likely had something wonky between the wireless and the wired connection somehow. What probably solved the issue was removing the wireless card.
The only thing DHCP would have to do with that is if somehow when the IP was renewed that the machine changed the network connection from wired to wireless or the other way. In any event, 'why' doesn't matter as long as it's fixed.