I have googled the heck out of this, and all I can find from the net and from the Cubase manual is that multitimbral or non-stereo plugins cannot be loaded via an Instrument track - so I reconfigured a few of the tracks via the VST instrument pane and routing the MIDI myself, rendered a different section of the project, and…nothing. Silence. In other areas only the first note of one of the plugins sounded, and the rest silence. So I have it running both ways at the moment, but no sound.
This is a new install of Cubase 5, 64-bit whereas I was using 32bit on my previous WinPC (7 Pro), this one is 7 Home premium. I updated to 5.5.3. Plugins are Korg legacy cell (with the blank GUI problem being ignored for now), Spector, Prologue, and Groove Agent ONE. Everything sounds fine while I am playing the project, but when I went to render a section to listen, there was only one long intro MIDI note on one of the plugins, and the rest silence. Everything else appears to be routed properly, and identically to projects I was doing on the other PC in Cubase 32-bit. Hardware is Mackie Onyx 400F, MIDI is MIDIPORT 8x8/s. Anything else I need to post let me know, and many TIA.