upload (ftp) won't work

I’m having 2 problems lately.

The first is that I can’t upgrade automagically anymore with ftp. WordPress gives me a “There was an error connecting to the server, Please verify the settings are correct”. When I try to connect with filezilla I can access everything like it should.

the second one is related to the first. I can’t upload any images anymore. When I try it the loading of the image starts but when it wants to write to the upload directory it says that it is unable due to an error.

The things I tried:
1. deactivated every plugin (via backend and also by creating a new plugin folder and renaming the original)
2. changing permissions to 775 and 777
3. Made a new wordpress blog on a subdomain to test but the problems are exactly the same.
4. Switched to the twentyten theme

Anybody has an idea for my problems? I think they are all ftp-related but I don’t know how to solve them. I’m not even sure that the problem lies with wordpress, maybe it’s my provider (the changed to ProFTP recently).