As far as I'm aware, a bookmark redirect poses no threat to your accounts in and of itself. All it does is find a certain bookmark and overwrite it's linked site. The problem is that they are often bundled with other malware in order to get on your computer in the first place. As such, I would highly recommend running a virus scan anyway even if the cache clearing works. And, depending on what the scan finds, think about changing passwords on any important sites. IE, bank sites and so on. Make sure you do the scan first. You want to get rid of any Keyloggers and/or Trojans first, or changing passwords will be pointless.