Virtualbox Redhat no valid drive

[sync]

Hi , all :

 Today I installed the RedHat 6 beta version on the Virtualbox ,
when entered the choosing  "Partitioning Type" section , I choosed any  one
of the following options:

1. Use entire drive
2. Replace existing Linux System
3. Use free space


The result was displayed the following error:

"No Drives Found
An error has occurres - no valid devices
were found on which to create new file
systems, Please check your hardware for
the cause of this problem"

Would anyone give me  some suggestions?

Thanks in advance ~

By the way , the Virtualbox Version is : 3.1.0 and my host system is CentOS
5.4 x86_64 .