When I update an app everything works fine. Android Market shows that the update was succesful and nothing is downloading. Also there are no items in "downloads". But when I reboot, the progress bar of the update that I've just installed reappears in the notification area and the download stars again and it finishes without installation. After another reboot it stats downloading the update again and so on. There is only one update that is being continuously downloaded after reboots and it is always the last update that I've made. I've already tried clearing Android Market's cache and checking if there are some items in downloads.
You need to clear the data of the Download Manager and of the Play Store. Go to:
Settings -> Applications -> All
Now for both of the apps mentioned above choose Clear Data and Clear Cache.
Try this. Select the application in the update queue and cancel the update. Do this for all pending items. They will still be in your My Apps queue marked download. Select one of these listings and choose update. It should finally finish the update process for that app. Do this all other apps marked update, one at a time.