|I know this is an old thread, and that you have probably sorted this out by now, but since this thread comes up high in Google searches I thought I'd post a solution anyway.|
The problem with Belkin routers is that even though you are allowed to save a new admin password regardless of it's length, the router actually only accepts 10 characters. For instance, if you have a password that's 13 characters long, the stupid router will let you save it without any warnings, but it actually removed the last three characters. So if your password was password12345, it only saves password12. You should be able to log in using only the first 10 characters.