Welcome to CB. Its a chore to get YM to work on your 8310 I tried but finally gave up. You can use the ATT media net or one of those services to access it or you can try loading an older version of YM.
It won't matter which version of yahoo messenger you have. AT&T doesn't provide you with the service books for yahoo messenger. It is either use their all in one messaging program, or go through the complicated process.
I use YIM on my BB as well and it works flawlessly. Follow the steps outlined in that thread and you will be up in no time. It's not difficult, but if you have any questions just ask.
Okay I posted this on another thread because I have a problem. I did not backup my Curve correctly then did the Yahoo service book and the rest of the steps. Now I have Yahoo on my Curve but no email. Any help?
Unfortunately you've lost the email you've already written. However, if you resend your service books from your carriers website (do a search on the forums for instructions on how to do this), you should get your email functionality back.