Usually if you install another app - any app - from the market it will refresh the My Apps section.
Also, if that doesn't work, you can try going into Talk, press menu->sign out. That will close Talk. Open it again (to sign in again), and then try the market.
Another thing to try if installing an app doesn't fix it is to open the dialer and dial:
*#*#CHECKIN#*#*
That should give you a notification that checkin was successful. Then look in the market and see if that fixed it.
After that, I'd try (from a home screen) settings->applications->manage applications, wait for the list to refresh, go to the entry "Market" and tap it, tap the button on that screen "clear cache".
You also may want to try restarting the phone.
Also know that occasionally the market has issues, and perhaps there is a temporary one going on right now.
I hope one of these things helps.