VixVM_Open() returns error "The datastore corresponding to the given datastore path is not found"

In one of our setup, VixVM_Open() API call returns error "The datastore corresponding to the given datastore path is not found."

The returned error code is 38.

The specified vmx path as input to VixVM_Open() is of the fornmat "[MyDatastore] MyVM/MyVM.vmx".

We have verified that the datastore "MyDatastore" and the vmx path "[MyDatastore] MyVM/MyVM.vmx" exists and a VM is using this path.

We don't suspect any problem with the code, as the same code works in other setups.

What can be the possible reasons of VixVM_Open() returning this error?

And where to look for to drill down the root cause?

PS: We called VixHost_Connect() API to connect to a vCenter server (5.1) and then used VixVM_Open() API to try to connect to a VM. But the later is returning error.

Thanks in advance.