cakewalk pro audio 9 playback timing problem

Does the slowdown happen on all the midi files you play or just this specific one?
What are you using for a synth to make the sounds for the midi?  Software synth?  External hardware synth?
Have you run the Wave Profiler (big button at lower left of DirectShow Audio)?
Have you checked the tempo map of the midi file?
--Larry

Hello i

Playing midi files using the Roland VSC synth should not put much of a strain on your system.
Since the slowdown also happens when you use VanBasco, the issue is not PA9.  (I'm assuming that you are using Pro Audio 9.03)

Try setting all the midi track output PORTs to Microsoft GS Wavetable SW Synth
That will get the Roland VSC out of the picture.
You might have to visit the PA9 menu Options>Midi Devices.... Output Ports and make sure that the GS Wavetable SW Synth is selected as a possible midi output.

--Larry