Ever since after the last mainetnance i cant login to the server anymore.
I login and choose for example Nereus and then the client crashes.

My brother tried and he can login on my PC and everything works perfect, but when i try on my pc or on his pc it crashes the client.

Can it be that my account got corrupt during maintenance yesterday?

before trying to log on again, you can check server status here first. when it's ok, try again. if you still have problem logging in, then, your issue maybe related to this post.