Yesterday I got problems with login to youtube plugin .. used this fix that worked to login:
https://www.youtube.com/watch?v=CVR1m6viAHE
Now playing VEVO videos I get this text in xbmc.log:
12:56:31 T:1568 NOTICE: Thread LanguageInvoker start, auto delete: false
12:56:31 T:1568 NOTICE: -->Python Interpreter Initialized<--
12:56:34 T:3608 NOTICE: Thread LanguageInvoker start, auto delete: false
12:56:34 T:3608 NOTICE: -->Python Interpreter Initialized<--
12:56:35 T:3608 NOTICE: Loading cookies from :'C:\\Users\\J\xc3\xb8rn\\AppData\\Roaming\\XBMC\\userdata\\addon_data\\plugin.video.youtube\\yt-cookiejar.txt'
12:56:35 T:3608 NOTICE: YouTube-4.4.8
12:56:35 T:3608 NOTICE: CommonFunctions-2.5.1
12:56:43 T:3608 NOTICE: links: 'dict'
12:56:44 T:456 ERROR: CCurlFile::Stat - Failed: HTTP response code said error(22) for
http://r2---sn-nxq3-xcwe.googlevideo.com...x%2F16.0.1
12:56:44 T:456 NOTICE: DVDPlayer: Opening:
http://r2---sn-nxq3-xcwe.googlevideo.com...x%2F16.0.1
12:56:44 T:456 WARNING: CDVDMessageQueue(player):

ut MSGQ_NOT_INITIALIZED
12:56:44 T:4460 NOTICE: Thread DVDPlayer start, auto delete: false
12:56:44 T:4460 NOTICE: Creating InputStream
12:56:44 T:4460 ERROR: CCurlFile::Stat - Failed: HTTP response code said error(22) for
http://r2---sn-nxq3-xcwe.googlevideo.com...x%2F16.0.1
12:56:44 T:4460 ERROR: CCurlFile::FillBuffer - Failed: HTTP response code said error(22)
12:56:44 T:4460 NOTICE: CCurlFile::FillBuffer - Reconnect, (re)try 1
12:56:44 T:4460 ERROR: CCurlFile::FillBuffer - Failed: HTTP response code said error(22)
12:56:44 T:4460 ERROR: CCurlFile::CReadState::Connect, didn't get any data from stream.
12:56:44 T:4460 ERROR: XFILE::CFileCache::Open - failed to open source <http://r2---sn-nxq3-xcwe.googlevideo.com/videoplayback?mt=1406199216&ratebypass=yes&key=yt5&id=o-AHAepQbA_HpQL2Z-5n3ynj7CVXEpvAT882xF8Li1oKZH&fexp=902408,922521,924222,927622,930821,934024,934030,936218,937432,946008,946505,948508&ipbits=0&mws=yes&itag=22&ms=au&mv=m&source=youtube&sver=3&expire=1406221005&sparams=id,ip,ipbits,itag,ratebypass,source,upn,expire&ip=78.157.109.14&upn=DHvXUgCum1c&signature=|User-Agent=Mozilla%2F5.0+%28Windows+NT+6.2%3B+Win64%3B+x64%3B+rv%3A16.0.1%29+Gecko%2F20121011+Firefox%2F16.0.1>
12:56:44 T:4460 ERROR: CDVDPlayer::OpenInputStream - error opening [
http://r2---sn-nxq3-xcwe.googlevideo.com...x%2F16.0.1]
12:56:44 T:4460 NOTICE: CDVDPlayer::OnExit()
12:56:44 T:456 ERROR: Playlist Player: skipping unplayable item: 0, path [plugin://plugin.video.youtube/?path=/root/video&action=play_video&videoid=saoOByAFy90]
12:56:44 T:824 NOTICE: Thread BackgroundLoader start, auto delete: false
12:56:44 T:456 NOTICE: CDVDPlayer::CloseFile()
12:56:44 T:456 NOTICE: DVDPlayer: waiting for threads to exit
12:56:44 T:456 NOTICE: DVDPlayer: finished waiting
12:56:44 T:456 NOTICE: CDVDPlayer::CloseFile()
12:56:44 T:456 NOTICE: DVDPlayer: waiting for threads to exit
12:56:44 T:456 NOTICE: DVDPlayer: finished waiting
12:56:44 T:3608 WARNING: CPythonInvoker(6, C:\Users\Jørn\AppData\Roaming\XBMC\addons\plugin.video.youtube\default.py): the python script "C:\Users\Jørn\AppData\Roaming\XBMC\addons\plugin.video.youtube\default.py" has left several classes in memory that we couldn't clean up. The classes include: class XBMCAddon::xbmcaddon::Addon,class XBMCAddon::xbmcaddon::Addon