Ok so then you have WSS 3.0. The groups aren't Domain groups they are local server groups.
Are you running a proxy server? you should disable auto detect proxy settings for your search account either way. You can do that by doing a Run as Domain\CrawlerServiceAccou
nt on Iexplore.exe and then disable automatic detect proxy in internet options.
Finally make sure that loopback is disabled you can read the instructions on how to do it here:
http://support.microsoft.com/kb/896861