I get the same error message. Login was tried via O2-Germany (UMTS), ActiveSync and WLAN. Neither one worked out. Using the www.evernote.com/m site works. I'm using the latest version of Evernote Mobile 3.3_64861.exe
I believe, categories are great. I used MS OneNote before and learned how great these categories are. It gives me the opportunity to split up masses of information and still know where they are. Besides this, Evernote would not have to load all the pictures of one notebook, just of one category. I guess, its performance would rise.