The Bold's browser does not support flash, so the only way you can stream youtube videos is by using m.youtube.com or any site similar to www.tinytube.net
There have been reports of people having problems with the Bold's 3G that is similar to what some iPhone users are experiencing. Although some people are experiencing no problems at all with their 3G coverage. So I say that if they network is fine then you should try exchanging the device for another Bold from your carrier if that is an option.
For the browser I would suggest making sure that the browser is set to page view if you are visiting regular web pages and checking all of the options under Browser Configuration to see if that helps.
~via BB (wap.pinstack.com)~