I recorded in Sonar a scratch track using my synthesizer and saved it as a WAV file.  I checked in both Sonar and my EMU sound card that they were set to 44.1 MH.  When the engineer plays the track in his studio he and my guitarist both say it sounds flat from the guitar that is tuned to 44.1.  I would appreciate any help.
 
Thanks,
 
Van

Sample rates are measured in KHz not Mega Hertz.

Guitars aren't tuned to sample rates. Unless he's talking about a track of guitar playing recorded at a sample rate of 44.1khz.

The fact that your synth is recorded at a sample rate of 44.1khz doesn't mean the synth is tuned to for example to a standard of tuning where A is 440 Hz. Maybe your synth is out of tune or the recorded guitar is out of tune,

Unless both instruments are tuned to the same pitch there's no guarantee. But that has nothing to do with sample rate.

Mike is correct
 
the sampling rate of the DAW and soundcard have nothing to do with the tuning of the synth.  if they think your synth is out of tune then there might be a setting on the synth you adjusted (sounds like you're using a hardware synth, so it would be a physical setting or knob on the synth depending on which synth you're using) to make it +/- from 440Hz = A.

 
Thank you for your help.  What would you suggest I do?  Can I try to retune the synthesizer to 440 KHz?  If I did that could I replay my current MIDI track back thru the retuned synth and record a new track that would tuned to 440?
 
I appreciate your time.
 

I suggest you clarify the problem with the engineer first so you know exactly what needs to be done. BTW A=440Hz not kHz. You could always check your synth to see if it has a tuning mechanism and see what it's set at.

It is far more common for a guitar to be out of tune than a synth. And before you go too much further, it would be a good idea to find out what the other instruments are actually tuned to. My guess is that the engineer and guitarist have decided that you have somehow created a sample rate mismatch, recording your synth at 48 KHz but saving the wave file at 44.1 KHz somehow. That is the only reason I can think of that they would even mention the sample rate.
 
That sample rate mismatch would also change the speed of the recording not just the pitch. Anyone who calls himself an audio engineer should have been able to change the sample rate on your file to fix that mismatch if that was the problem, with only minimal loss of quality. I actually do not know how to do that in Sonar, but it is easy enough in Audacity (free download)--just import and change the rate under set rate in the dropdown menu that appears when you click the black triangle to the left of the tracks), then tracks>re-sample and then export as a new wave file (WAV (Microsoft) signed 16 bit PCM). 
 
To figure out why you had the problem in the first place it would be helpful to know more about exactly what you were doing to get there. What kind of synth are you using? Is it being controlled by Sonar of is it just that the synth output is being recorded into Sonar?