If you ever find that one of your web parts are erroring on a particular site because some custom web part is throwing an exception and stops the site page from loading then one of the first thing you should do is try adding contents=1 to the end of the url for the site you are trying to access.
http://<SharePoint Server>/Pages/<Site Name>/default.aspx?contents=1
This will load a web part maintenance page for that site, from here you can remove the erroring web part from the site page.