Failed to open a session for the virtual machine

[windstory]

I got an error at openning windows 7 virtual machine on host windows 8.1 x64.

Failed to open a session for the virtual machine _YoungAhWork.

No error info.

Result Code: E_FAIL (0x80004005)
Component: ProgressProxy
Interface: IProgress {c20238e4-3221-4d3f-8891-81ce92d9f913}

Please let me know how to resolve this error.
Thanks in advance.