I just upgraded to Sonar 8.5 Producer from Sonar 6 and haven't worked the bugs out.
I created a MIDI track and ran RealPiano from it
I created an audio track and tried to record guitar to go with the MIDI piano
But the MIDI piano playback during recording was delayed almost one full measure.
Any suggestions?
 

How did you find a copy of 8.5 you lucky dog?  Any how, You should always leave one blank measure at the beginning,
Just drag the MIDI track over one measure and try again.
Also make sure you are monitoring via the M Audio not your computer sound card.

http://www.amazon.com/Sonar-8-5-Studio-OLD-VERSION/dp/B001GIDME6

Is the project playing but the soft synth audio doesn't start right away, or is there a delay in the project starting? The Metronome Count-In can delay the start of a project playing with no audible metronome if set wrong. Do you use the Metronome and can hear it?

If I had my Metronome set like in the image below, I would have a 1 measure delay before the project starts playing when I click the record button, but wouldn't hear anything because it is set to Midi and I don't have a Midi device connected. To check your Metronome settings go to Options>Project>Metronome Tab.

Try hitting play then record.  I had the exact same problem on sonar 8.5/64 under Windows 7 64 bit.  Tempo changes occur about a measure late also which really makes it confusing. Fortunately I accidentally hit play then record while troubleshooting and discovered a reasonable workaround. 

ScreamerBob
Try hitting play then record.  I had the exact same problem on sonar 8.5/64 under Windows 7 64 bit.  Tempo changes occur about a measure late also which really makes it confusing. Fortunately I accidentally hit play then record while troubleshooting and discovered a reasonable workaround. 

 Welcome to the forum Screamer, but this thread is four years old. I'm sure the problem is solved :o)