I have the same problem on 12.04 up to date on a Samsung N310.
This started a few days ago. It is very annoying, as often I click on the launcher icon and instead of bringing the document that is already opened, it opens a new blank document.
So the document is often not visible on the launcher or in alt+tab, but it is visible when using the spread function (either with super+Z or with a hotcorner set by Ubuntu Tweak).
I sometimes also get an extra icon at the bottom of launcher (the icons don't merge for some reason).
I have the same problem on 12.04 up to date on a Samsung N310.
This started a few days ago. It is very annoying, as often I click on the launcher icon and instead of bringing the document that is already opened, it opens a new blank document.
So the document is often not visible on the launcher or in alt+tab, but it is visible when using the spread function (either with super+Z or with a hotcorner set by Ubuntu Tweak).
I sometimes also get an extra icon at the bottom of launcher (the icons don't merge for some reason).