I’m having the exact same problem connecting to or creating a floating window session (virtual desktop sessions *do* work). My session logs are functionally identical to what ecerulm posted. Server is running on RHEL5 using the following rpm versions:
nxnode-3.5.0-3
nxclient-3.5.0-6
nxserver-3.5.0-9
Running NoMachine 4.0.366 client on Windows 7 x64.