Xperia X10 Reset Market Application
When moving applications around or when installing applications without the use of the Market application, the Market application will not be able to display update notifications for any of those applications.
To solve this, reset the Market application with
$ su - # busybox rm -rf /data/data/com.android.vending
The next time the Market application is used, it will rescan all your installed applications and thus making sure they're all attached to the market properly.