Merry Christmas and Happy New Year to you as well!
I suspect our use of the adapter is related. Our adapter is nothing more than the ASP.NET CSS Control Adapter changed to our namespace.
Actually there are only a few places where we use GridView directly in mojoPortal,most places I'm using YuiGridView which inherits from GridView.
You can disable the adapter by commenting out all references like this in App_Browsers/CSSFriendlyAdapters.browser
However, it requires a re-compile for changes to take effect.
Alternatively, maybe the link above can provide you enough information to customise it with the adapters enabled. It does produce better quality markup using the adapter.
What I could do is create a custom GridView name mojoGridView that does nothing but inherit from GridView then I could specify the adapter for the mojoGridView without it applying to normal GridView. This way users who want the adapter could use mojoGrdiView and users who don't could use the normal GridView. Currently since I have GridView specified in the .browser file I think it also affects sub classes. Let me know if that would be helpful and if so I will make that change for the next release.
Hope it helps,