Can't connect to YouTube on 4.2.1 version it's been jailbroken too

If your iphone is not currently jailbroken, then I am afraid to say that it is not possible. If your phone is jailbroken, go to cydia, add the ihacks repo, then install yourtube 2, it is a built in youtube video downloader for your youtube app.

This can happen with Jailbroken iPhones.
Try this: http://iphoners.org/cannot-connect-to-youtube/
or Google search "cannot connect youtube jailbroken" There are several reasons that it happens.
You can load MxTube instead.

Hi panggalory,
Is your iPhone 4 factory unlocked or jailbroken then unlocked?
Either way, please read the following:

• Make sure that the USB cable is in good condition
• Try connecting in different USB ports of your system
• Reinstall iTunes to the latest version http://apple.com/itunes
• Try connecting your phone in some other computer
  
  

The above solutions should work because I myself have faced this problem and these have worked for me. If it still doesn't work, the please let me know.
-Pragith

Find your solution from the list,
Apple Iphone Smartphone
Codes:

• Unlock Code,
• Password,
• Puk Code,
• Lock Code,
• Other Codes.

Software & Hardware Problems

• Software Problems (Hang, Youtube etc.)
• Hardware Problems (Display, Charging etc.)

Find Solutions for other Apple Products:
Apple Iphone 3G
Apple iPod Touch Digital Media Player

Hi Leon6253, Ive been having the same problem, noticed it about 4 days ago. On my iPhone 3Gs, 32gig, I have 2 pages of "saved to homescreen" icons of specific & individual music videos at YouTube. Previously they all worked FINE!! (I loved having the tiny pics/icons of whichever singer & their specific URL Direct to their song on my home screens). I would simply tap the icon/pic & YouTube would automatically open up & start playing. NOW, ZILCH !!! Instead it takes me to a YouTube page for that particular song but there is NO VIDEO window & NO BUTTON to "play video"!! Just a white square where the video normally is. SO WHO SCREWED THIS UP? YOUTUBE & GOOGLE, or what??? This is very distressing. Not only does the video NOT PLAY, but it also automatically changes my prior icon/picture into a RED icon with a "play video" type button. But if you tap on it, STILL NO VIDEO, but it merely goes to the page for the video &, as described above, there is NO VIDEO not PLAY button on the webpage!! Grrrrr. Sorry, I don't have a solution, just wanted the world to know you are not alone.

To fix this problem , add http://cydia.iphoneil.net/ as a source to your cydia app and install the "Push Fix" app

Ignore the SPAM post on this question,

This problem normally only affects Jailbroken iPhones. To fix this problem add http://cydia.iphoneil.net/ as a source to your cydia app and install the "Push Fix" app

Is your phone jailbroken? Otherwise, have you upgraded to the newest firmware version?
If it is jailbroken, try doing this: http://limitededitioniphone.com/youtube-not-working-on-your-iphone-steps-to-fix/
Otherwise have a look here: http://discussions.apple.com/thread.jspa?messageID=6813270