Based on the process given, I'm guessing you mistyped the new explorer filename, and Windows doesn't have anything to load now (If the filename is wrong, it's got nothing to load for the shell.). Here's a quote from that page:
"It appeared to be working except my desktop never fully loaded. I got this message saying that Windows Explorer had encountered a problem and needed to close. Blah, blah, blah, you know the drill. So I restart. Same thing. I thought I was in big trouble until I tried ctrl-alt-del. Success! I was able to start a new task (regedit), point my Shell back to explorer.exe, and restart. Low and behold, after I entered my password, my desktop came up and everything was normal. SP2 has worked like a charm ever since."
That should work (CTRL+ALT+DELETE) to run explorer.exe (or whatever you changed the filename to) since the CTRL+ALT+DELETE dialog box can start a new task (just point it to the filename).
So long explanation short, try CTRL+ALT+DELETE to start a new task.