I have an interesting thing going on.  I've got a site running in a temp location just fine for me.  Everything works just as it should.  However when I use a friends laptop to show him the site it doesn't work right. Menus with sub menus don't close as you progress down the links. Furthermore some pages won't even load up; very weird.  He informed me he had upgraded to IE-8 which was causing him all kinds of problems with sites like Yahoo and others.  I checked another system that had upgraded to IE-8 with the same results. Has anyone else experienced this and if so is there a workaround?

The Core skin works great in IE8 so you can either fix up your skin/menu system like the core one or use the IE8 compatability tag like Sebastian suggested.  The tag is to handle the quirks that IE6 and 7 have.

it depends on the skin version - the ones provided with DNN 4.9.x/5.0.x work perfectly in quirks mode but have some glitches in IE8 mode.