Weird accounts

Hello,

For some reason we get weird accounts registered.
Plugins we use :

bbpress
login with ajax
members
new user aprove
SI captcha anti spam
spammer blocker
wp members

And still wierd fake account with even weirdest names.
Anyone have a clue howcome and how to take care of this?

Registration was set open on the website, but even with the new user approve new accounts have been made!

Help would be appriciated