Ever since Google updated the Market to 3.1.5, I've been having problems. I don't have "missing" apps (all my apps appear on the download page), however,
1. I have apps appearing with updates and then when I click on them to update, it shows no update (the only choices are to open the app or uninstall it).
2. Navigation is really slow. First clicking on the Market icon, it takes about 30 seconds before the homepage appears. From there, trying to update apps slows down even further. When I go to the "my apps" page, clicking on an app to update it and it takes anywhere from 3-5 minutes before the app info page to appear. If I click on the update icon, it takes another 3-5 minutes before the confirmation page to initiate the download appears. Then clicking on the confirmation, it basically attempts loading and then times out and the Market app force closes.
3. Apps that I have configured to auto-update are not. They show up as manual updates.