I started a thread about this exact problem on Tuesday. YouTube good on WiFi, no go on 3G. Nothing I tried fixed it. About halfway through Wednesday afternoon it was working just fine on 3G again.
Of note, on Wednesday I was having calendar sync issues in the am. I did about 15 re-boots and after that YouTube worked again. Coincidence? Maybe, but it works now and that's all that matters.
Posted from my CrackBerry at wapforums.crackberry.com
Posted from my CrackBerry at wapforums.crackberry.com