I am having the same issue. My Yahoo Mail stopped working probably around mid night last night. It had been running on GB 2.3.3 for a couple of weeks. I upgraded to this 6/21/11 release this morning. The problem is still there.
Update: my Yahoo Mail problem is that it does not get new mail from the server. The last one I got was around 10pm last night. If I use my PC to retrieve Yahoo mail, I get lots of them.
I also noticed that my FB shows empty content on the News Feed. If I use a PC to see FB, I can see lots of updates. But on Evo 4G, it shows empty.
Try checking the check frequency settings for your account on the EVO.
sometimes after updating, things get defaulted back to factory not your custom settings.
I did the "fix" today, then updated the voice search app, but my phone still doesn't recognize voice under noisy conditions, where previously it had no problems at all. As someone stated earlier, this is a safety issue to me because I always used voice when setting locations for my GPS. Now, I have to be at a stoplight or risk typing in an address while driving. I really hope they fix this soon because I used voice input a LOT for GPS. 