No DHCP when using Linksys WRE54G Range Expander

I have a mixed environment of PC's and Mac's. My Linksys wireless router doesn't have a strong enough signal to reach all the areas I need it, so I bought a Linksys WRE54G (v2.0) Range Expander. I now get great expanded wireless coverage, but none of my Mac's (running OS X v10.4) can get an IP address from DHCP when connected wirelessly through the range expander. All my PC-based laptops work fine (wired and wireless), as do my wired Mac's. The wireless Mac's do get an IP address from DHCP when the WRE54G is turned off (when I move them close enough to the wireless router). Also, the Mac's work through the range expander if I configure them with static IP addresses.

Any ideas?