Just noticed you are using 10.4.2. Improvements/changes have been made to Safari since this version. This may be why the log-in is not cooperating for you, yet working for the Admin.
Upgrade to 10.4.7 using the
combined update. After the install/restart, repair permissions using Disk Utility. Once you have upgraded, go to System Preferences>Software Update. See if there is any security upgrade you may be missing. If there are any security upgrades, again repair permissions after the restart.
iMac G5 Rev C 20" 2.5gb RAM 250 gb HD/iBook G4 1.33 ghz 1.5gb RAM 40 gb HD Mac OS X (10.4.7) LaCie 160gb d2 HD Canon i960 printer