[otrs] otrs 3.0.5 session id is invalid

HI, I am new user to otrs. Please help me for this problem. 1. after a fresh installation of otrs ver 3.0.5-b1 in Centos 5.5 using the otrs rpm version. I tried to login as root@localhost and root, i get msg "session id is invalid". I had tried to reboot my system but still same. i also check mysql otrsdb and see table user - there is root@localhost. look forward to hearing from you. thanks. Best Regards, Jason *** Reclaim Your Freedom, use Free & Open Source Software - Be Open Standard Compliance. ***