Audio mismatch?

Hi folks

Yep, I'm back again. And unfortunately, I really don't believe this to be a Premiere Pro problem per se. I really think it's more of a Vimeo issue. Hoping some of you seasoned folks may have some insight or offer some advice.

I'm creating some videos for a minister friend and I'm uploading to Vimeo. He presents the videos on his church's site from Vimeo. He provided me with an intro clip and an outro clip and my role is to glue them together and massage the video a bit. Pretty basic stuff.

I finish and render and all seems fine. I used the "Vimeo preset" in Premiere Pro to render. Then I upload to Vimeo.

Problem is, he's asking me about the audio slightly lagging or mismatching the video when he views. Asked it it was just him and his PC or what. He uses Mac. I think his connection is broadband (cable modem) but not sure. I know I have broadband (cable modem) and I had my wife test from her PC. She also says the mismatch is "pretty bad". So I rendered a different vid and had her view on my own PC before uploading. She said it was perfect. So this tends to point at the process of Vimeo encoding the video or maybe not sending it fast enough. I'm not sure.

So wondering how best to troubleshoot this. I know from working with Adobe Captivate that if you save that out and upload to YouTube we see audio mismatch and the typical solution was to ensure you chose constant bitrate as opposed to Variable. But Vimeo site says VBR is preferred. I did try a constant setting from PP but it didn't seem to make a discernable difference.

What to check?

Thanks... Rick