Setting a static lease on my Router also fixed the issue for me and is much better than setting a static IP address on the Galaxy S.I've also run into this and fixed it by setting a static IP. However didn't want to do this on the Tab as it would require me to remember to change it if using outside my home. A better solution I found was to setup a static IP on my router. Basically I recorded the MAC address of the TAB on my router and had it hand out the same IP address each time. This works like a charm and I can keep the Tab set to DHCP.
Note you can also have the tab forget a network by just deleting it. It works but you do indeed have to set it up and delete like 3 or 4 times. This eventually worked for me before I setup the static on my router. I really did not want to do a hard reset so I kept trying until it worked. I believe it was the 4 time it eventually forgot the original settings.