This is because while the Dynamic Memory is great for general servers, it can't accomodate for SharePoint timer jobs and other internal activities. When SharePoint 'wakes up' to do something, the memory isn't allocated fast enough so SharePoint thinks the server is dead.
I personally discovered this after taking over a farm setup by Microsoft (a Hyper-V expert). Despite a perfect SharePoint installation, the farm was constantly having issues; odd errors, services failing, etc. After many, many hours of testing I finally proved to them what the issue was.
So word to the wise - DON'T use it, regardless of what anyone says!!