I was working through the introductory sharepoint 2010 labs, and deployed a bad Visual Web Part (It was missing this closing tag: </SharePoint:SPGridView>). I didn't know about this being a problem (since the compile was fine) until after the deployment. When I added the new web part to the home page, at intranet.contoso.com, it created an error. The home page became wacked. When I tried to put the home page in edit mode, it alerts me to the error, and refuses to go into edit mode, so that I might remove the bad web part.
I then fixed the error in Visual Studio and re-deployed (not sure if this was the right procedure or not, but there was no complaints from Visual Studio). However, I still can't get into edit mode. Somehow, the re-deployment failed.
If I can somehow undo the deployment of the Visual Web Part, then perhaps I will get a fixable error in the home page (something along the lines fo a 'missing reference'), then if I remove any such reference in that page, I may be able to re-deploy a good component, and then set a reference to the good component (i.e., Visual Web Part).