Message: "Failed opening MIDI system" on startup (Win7/64)

If your startup log reads like this, there is probably a conflict with the ASIO4ALL driver under Windows 7 64bit:

Linking to external MIDI libraries
exception occured #(3221225477 0)
Failed opening MIDI system [exception occured #(3221225477 0)]
Failed opening MIDI system [error: 2]. Possibly built-in GS Wavetable Synth is blocked from using your audio driver.

You might need to disable the internal Microsoft GS Wavetable Synth, which attempts to use the driver. The current release of ASIO4ALL can only serve a single client (synth, DAW) at a time, so if you have a DAW running, HN2/Synfire Pro can not start if the synth is still enabled. Here's a forum post that discusses how to disable the GS synth:

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