> 1.5 Mbps auto-adjust?  I'm not familiar with that.  What service provider
> offers this?  (A link to service info page would be helpful.
>
> I would think that by limiting both the uplink and downlink speeds to about
> 1/2 of the overall bandwidth, it would probably work, since the ISP wouldn't
> be adjusting anything.  (Though it sounds like you've already tried this)
>
>   
Yes, you are correct about the bandwidth - except I don't think the 
upload is 500 Mbps ;-P

Yes, I did try splitting it in half, and I tried using much lower values 
(500Kbit/s incoming, 350Kbit/s outgoing) as well.

My provider is a local company that pretty much only services this town. 
Additionally, our link is wireless if that matters for some reason.

> Could this be related to MTU size through the VPN tunnel?
I don't have a clue, nor do I know how to find this out! I have tried 
lowering the MTU size of the WAN link based on something I had read, but 
it made no difference that I could tell.

Thanks for the suggestions,
Andy