There was a security exploit found in SMF where bots/hackers have been trying to collect users' passwords. A dictionary attack is when someone or a bot uses a script to try and login into your account and use a lot of dictionary words to guess your password. Until this site has been upgraded to RC4 or RC5, you may experience logouts when the hackers are trying to gain entry into your account. You can just log back in without any worries, if you have a strong password. To prevent your account from being hijacked, it is HIGHLY suggested that all users make sure that their passwords have a strong strength.
That means that you should use, at least, one special character ( such as !, @, %, etc.) and contain a mixture of letters and numbers as well as upper and lowercase letters. Do not use something that is easily guessed such as your birthday, pet's name, social security number, etc.
Please note that if you use one password for all of the websites that you visit and the bots guess it, they can take over your account here and those other sites. This does include bank accounts, etc.